diff --git a/main/inc/lib/multibyte_string_functions.lib.php b/main/inc/lib/multibyte_string_functions.lib.php
index 3997927762..07aaffff60 100644
--- a/main/inc/lib/multibyte_string_functions.lib.php
+++ b/main/inc/lib/multibyte_string_functions.lib.php
@@ -16,9 +16,9 @@
  * Notes:
  *
  * 1. For all the functions from this library witn optional encoding
- * parameters the system's encoding is assumed, i.e. the value that is
- * returned by api_get_setting('platform_charset') or the value of the
- * global variable $charset.
+ * parameters, the system's encoding is assumed by default, i.e. the
+ * value that is returned by api_get_setting('platform_charset') or 
+ * the value of the global variable $charset.
  *
  * 2. In other aspects, most of the functions in this library try to copy
  * behaviour of some core PHP functions and some functions from the
@@ -37,6 +37,8 @@
  * When encodings to be used are not supported by mbstring, this library
  * is able to exploit the PHP iconv extesion, which in this case should
  * be activated too.
+ * 
+ * 5. TODO: Functions that were not used may be removed from this library.
  */
 
 /**
@@ -51,7 +53,7 @@
  * @param string $to_encoding		The encoding that $string is being converted to.
  * @param string $from_encoding		The encoding that $string is being converted from. If it is omited, the platform character set is assumed.
  * @return string					Returns the converted string.
- * This function is aimed to replace mb_convert_encoding() for human-language strings.
+ * This function is aimed at replacing the function mb_convert_encoding() for human-language strings.
  * @link http://php.net/manual/en/function.mb-convert-encoding
  */
 function api_convert_encoding($string, $to_encoding, $from_encoding = null) {
@@ -77,7 +79,7 @@ function api_convert_encoding($string, $to_encoding, $from_encoding = null) {
  * @param string $string			The string being converted.
  * @param string $from_encoding		The encoding that $string is being converted from. If it is omited, the platform character set is assumed.
  * @return string					Returns the converted string.
- * This function is aimed to replace utf8_encode() for human-language strings.
+ * This function is aimed at replacing the function utf8_encode() for human-language strings.
  * @link http://php.net/manual/en/function.utf8-encode
  */
 function api_utf8_encode($string, $from_encoding = null) {
@@ -103,7 +105,7 @@ function api_utf8_encode($string, $from_encoding = null) {
  * @param string $string			The string being converted.
  * @param string $to_encoding		The encoding that $string is being converted to. If it is omited, the platform character set is assumed.
  * @return string					Returns the converted string.
- * This function is aimed to replace utf8_decode() for human-language strings.
+ * This function is aimed at replacing the function utf8_decode() for human-language strings.
  * @link http://php.net/manual/en/function.utf8-decode
  */
 function api_utf8_decode($string, $to_encoding = null) {
@@ -169,7 +171,7 @@ function api_to_system_encoding($string, $from_encoding = null, $check_utf8_vali
  * @param int $quote_style		The quote style - ENT_COMPAT (default), ENT_QUOTES, ENT_NOQUOTES.
  * @param string $encoding		The encoding (of the input string) used in conversion. If it is omited, the platform character set is assumed.
  * @return string				Returns the converted string.
- * This function is aimed to replace htmlentities() for human-language strings.
+ * This function is aimed at replacing the function htmlentities() for human-language strings.
  * @link http://php.net/manual/en/function.htmlentities
  */
 function api_htmlentities($string, $quote_style = ENT_COMPAT, $encoding = null) {
@@ -200,7 +202,7 @@ function api_htmlentities($string, $quote_style = ENT_COMPAT, $encoding = null)
  * @param int $quote_style		The quote style - ENT_COMPAT (default), ENT_QUOTES, ENT_NOQUOTES.
  * @param string $encoding		The encoding (of the result) used in conversion. If it is omited, the platform character set is assumed.
  * @return string				Returns the converted string.
- * This function is aimed to replace html_entity_decode() for human-language strings.
+ * This function is aimed at replacing the function html_entity_decode() for human-language strings.
  * @link http://php.net/html_entity_decode
  */
 function api_html_entity_decode($string, $quote_style = ENT_COMPAT, $encoding = null) {
@@ -229,17 +231,26 @@ function api_xml_http_response_encode($string, $from_encoding = null) {
 	return $string;
 }
 
+/**
+ * ----------------------------------------------------------------------------
+ * Common multibyte string functions
+ * ----------------------------------------------------------------------------
+ */
 
-//----------------------------------------------------------------------------
-//               Common multibyte string functions
-//----------------------------------------------------------------------------
-
-// Regular expression match with multibyte support.
-// See http://php.net/manual/en/function.mb-ereg
+/**
+ * Executes a regular expression match with extended multibyte support.
+ * By default this function uses the platform character set.
+ * @param string $pattern	The regular expression pattern.
+ * @param string $string	The searched string.
+ * @param array $regs		If specified, by this passed by reference parameter an array containing found match and its substrings is returned.
+ * @return mixed			1 if match is found, FALSE if not. If $regs has been specified, byte-length of the found match is returned, or FALSE if no match has been found.
+ * This function is aimed at replacing the functions ereg() and mb_ereg() for human-language strings.
+ * @link http://php.net/manual/en/function.ereg
+ * @link http://php.net/manual/en/function.mb-ereg
+ */
 function api_ereg($pattern, $string, & $regs = null) {
 	$count = func_num_args();
 	$encoding = api_mb_regex_encoding();
-
 	if (api_mb_supports($encoding)) {
 		if ($count < 3) {
 			return @mb_ereg($pattern, $string);
@@ -254,7 +265,7 @@ function api_ereg($pattern, $string, & $regs = null) {
 			$result = @mb_ereg(api_utf8_encode($pattern, $encoding), api_utf8_encode($string, $encoding));
 		} else {
 			$result = @mb_ereg(api_utf8_encode($pattern, $encoding), api_utf8_encode($string, $encoding), $regs);
-			$regs = api_array_utf8_decode($regs, $encoding);
+			$regs = _api_array_utf8_decode($regs, $encoding);
 		}
 		api_mb_regex_encoding($encoding);
 		return $result;
@@ -267,11 +278,25 @@ function api_ereg($pattern, $string, & $regs = null) {
 	}
 }
 
-// Replace regular expression with multibyte support.
-// See http://php.net/manual/en/function.mb-ereg-replace
+/**
+ * Scans string for matches to pattern, then replaces the matched text with replacement, with extended multibyte support.
+ * By default this function uses the platform character set.
+ * @param string $pattern		The regular expression pattern.
+ * @param string $replacement	The replacement text.
+ * @param string $string		The searched string.
+ * @param string $option		Matching condition.
+ * If i is specified for the matching condition parameter, the case will be ignored.
+ * If x is specified, white space will be ignored.
+ * If m is specified, match will be executed in multiline mode and line break will be included in '.'.
+ * If p is specified, match will be executed in POSIX mode, line break will be considered as normal character.
+ * If e is specified, replacement string will be evaluated as PHP expression.
+ * @return mixed				The modified string is returned. If no matches are found within the string, then it will be returned unchanged. FALSE will be returned on error.
+ * This function is aimed at replacing the functions ereg_replace() and mb_ereg_replace() for human-language strings.
+ * @link http://php.net/manual/en/function.ereg-replace
+ * @link http://php.net/manual/en/function.mb-ereg-replace
+ */
 function api_ereg_replace($pattern, $replacement, $string, $option = null) {
 	$encoding = api_mb_regex_encoding();
-
 	if (api_mb_supports($encoding)) {
 		if (is_null($option)) {
 			return @mb_ereg_replace($pattern, $replacement, $string);
@@ -295,9 +320,9 @@ function api_ereg_replace($pattern, $replacement, $string, $option = null) {
 }
 
 // This is a helper callback function for internal purposes.
-function api_array_utf8_decode($variable, $encoding) {
+function _api_array_utf8_decode($variable, $encoding) {
 	if (is_array($variable)) {
-		return array_map('api_array_utf8_decode', $variable, $encoding);
+		return array_map('_api_array_utf8_decode', $variable, $encoding);
 	}
     if (is_string($var)) {
     	return api_utf8_decode($variable, $encoding);
@@ -305,12 +330,20 @@ function api_array_utf8_decode($variable, $encoding) {
     return $variable;
 }
 
-// Regular expression match ignoring case with multibyte support.
-// See http://php.net/manual/en/function.mb-eregi
+/**
+ * Executes a regular expression match, ignoring case, with extended multibyte support.
+ * By default this function uses the platform character set.
+ * @param string $pattern	The regular expression pattern.
+ * @param string $string	The searched string.
+ * @param array $regs		If specified, by this passed by reference parameter an array containing found match and its substrings is returned.
+ * @return mixed			1 if match is found, FALSE if not. If $regs has been specified, byte-length of the found match is returned, or FALSE if no match has been found.
+ * This function is aimed at replacing the functions eregi() and mb_eregi() for human-language strings.
+ * @link http://php.net/manual/en/function.eregi
+ * @link http://php.net/manual/en/function.mb-eregi
+ */
 function api_eregi($pattern, $string, & $regs = null) {
 	$count = func_num_args();
 	$encoding = api_mb_regex_encoding();
-
 	if (api_mb_supports($encoding)) {
 		if ($count < 3) {
 			return @mb_eregi($pattern, $string);
@@ -325,7 +358,7 @@ function api_eregi($pattern, $string, & $regs = null) {
 			$result = @mb_eregi(api_utf8_encode($pattern, $encoding), api_utf8_encode($string, $encoding));
 		} else {
 			$result = @mb_eregi(api_utf8_encode($pattern, $encoding), api_utf8_encode($string, $encoding), $regs);
-			$regs = api_array_utf8_decode($regs, $encoding);
+			$regs = _api_array_utf8_decode($regs, $encoding);
 		}
 		api_mb_regex_encoding($encoding);
 		return $result;
@@ -338,11 +371,25 @@ function api_eregi($pattern, $string, & $regs = null) {
 	}
 }
 
-// Replace regular expression with multibyte support ignoring case.
-// See http://php.net/manual/en/function.mb-eregi-replace
+/**
+ * Scans string for matches to pattern, then replaces the matched text with replacement, ignoring case, with extended multibyte support.
+ * By default this function uses the platform character set.
+ * @param string $pattern		The regular expression pattern.
+ * @param string $replacement	The replacement text.
+ * @param string $string		The searched string.
+ * @param string $option		Matching condition.
+ * If i is specified for the matching condition parameter, the case will be ignored.
+ * If x is specified, white space will be ignored.
+ * If m is specified, match will be executed in multiline mode and line break will be included in '.'.
+ * If p is specified, match will be executed in POSIX mode, line break will be considered as normal character.
+ * If e is specified, replacement string will be evaluated as PHP expression.
+ * @return mixed				The modified string is returned. If no matches are found within the string, then it will be returned unchanged. FALSE will be returned on error.
+ * This function is aimed at replacing the functions eregi_replace() and mb_eregi_replace() for human-language strings.
+ * @link http://php.net/manual/en/function.eregi-replace
+ * @link http://php.net/manual/en/function.mb-eregi-replace
+ */
 function api_eregi_replace($pattern, $replacement, $string, $option = null) {
 	$encoding = api_mb_regex_encoding();
-
 	if (api_mb_supports($encoding)) {
 		if (is_null($option)) {
 			return @mb_eregi_replace($pattern, $replacement, $string);
@@ -364,24 +411,14 @@ function api_eregi_replace($pattern, $replacement, $string, $option = null) {
 	}
 }
 
-// This function returns a selected by position character of a string.
-function api_get_character($string, $position, $encoding = null) {
-	if (empty($encoding)) {
-		$encoding = api_mb_internal_encoding();
-	}
-	return api_substr($string, $position, 1, $encoding);
-}
-
-// This function returns an array containing all characters of a string.
-function api_get_characters($string, $encoding = null) {
-	if (empty($encoding)) {
-		$encoding = api_mb_internal_encoding();
-	}
-	return api_str_split($string, 1, $encoding);
-}
-
-// Makes a string's first character lowercase.
-// See http://php.net/manual/en/function.lcfirst
+/**
+ * Returns a string with the first character lowercased if that character is alphabetic.
+ * @param string $string	The input string.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			The result string.
+ * This function is aimed at replacing the function lcfirst() for human-language strings.
+ * @link http://php.net/manual/en/function.lcfirst
+ */
 function api_lcfirst($string, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -389,27 +426,19 @@ function api_lcfirst($string, $encoding = null) {
     return api_strtolower(api_substr($string, 0, 1, $encoding), $encoding) . api_substr($string, 1, api_strlen($string, $encoding), $encoding);
 }
 
-// Puts a prefix into a string.
-// The input variables could be arrays too.
-function api_prefix($string, $prefix) {
-	if (is_array($string)) {
-		if (is_array($prefix)) {
-			return array_map('api_prefix', $string, $prefix);
-		} else {
-			return array_map('api_prefix', $string, array_fill(0 , count($string) , $prefix));
-		}
-	}
-	if (is_array($prefix)) {
-		$prefix = implode('', $prefix);
-	}
-	return $prefix.$string;
-}
-
-// Splits string into array by regular expression.
-// See http://php.net/manual/en/function.mb-split
+/**
+ * Splits a multibyte string using regular expression pattern and returns the result as an array.
+ * By default this function uses the platform character set.
+ * @param string $pattern	The regular expression pattern.
+ * @param string $string	The string being split.
+ * @param int $limit		If this optional parameter $limit is specified, the string will be split in $limit elements as maximum.
+ * @return array			The result as an array.
+ * This function is aimed at replacing the functions split() and mb_split() for human-language strings.
+ * @link http://php.net/manual/en/function.split
+ * @link http://php.net/manual/en/function.mb-split
+ */
 function api_split($pattern, $string, $limit = null) {
 	$encoding = api_mb_regex_encoding();
-
 	if (api_mb_supports($encoding)) {
 		if (is_null($limit)) {
 			return @mb_split($pattern, $string);
@@ -419,13 +448,12 @@ function api_split($pattern, $string, $limit = null) {
 	}
 	elseif (api_iconv_supports($encoding)) {
 		api_mb_regex_encoding('UTF-8');
-
 		if (is_null($limit)) {
 			$result = @mb_split(api_utf8_encode($pattern, $encoding), api_utf8_encode($string, $encoding));
 		} else {
 			$result = @mb_split(api_utf8_encode($pattern, $encoding), api_utf8_encode($string, $encoding), $limit);
 		}
-		$result = api_array_utf8_decode($result, $encoding);
+		$result = _api_array_utf8_decode($result, $encoding);
 		api_mb_regex_encoding($encoding);
 		return $result;
 	} else {
@@ -437,21 +465,33 @@ function api_split($pattern, $string, $limit = null) {
 	}
 }
 
-// This is a multibyte replacement of str_ireplace().
-// See http://php.net/manual/en/function.str-ireplace
-// TODO: To be revised an to be checked.
+/**
+ * This function returns a string or an array with all occurrences of search in subject (ignoring case) replaced with the given replace value.
+ * @param mixed $search		String or array of strings to be found.
+ * @param mixed $replace	String or array of strings used for replacement.
+ * @param mixed $subject	String or array of strings being searced.
+ * @param int $count		The number of matched and replaced needles will be returned in count, which is passed by reference. 
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return mixed			String or array as a result.
+ * Notes:
+ * If $subject is an array, then the search and replace is performed with every entry of subject, the return value is an array.
+ * If $search and $replace are arrays, then the function takes a value from each array and uses it to do search and replace on subject.
+ * If $replace has fewer values than search, then an empty string is used for the rest of replacement values.
+ * If $search is an array and $replace is a string, then this replacement string is used for every value of search.
+ * This function is aimed at replacing the function str_ireplace() for human-language strings.
+ * @link http://php.net/manual/en/function.str-ireplace
+ * TODO: To be revised and to be checked.
+ */
 function api_str_ireplace($search, $replace, $subject, & $count = null, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
 	}
-
 	if (is_array($subject)) {
 		foreach ($subject as $key => $val) {
 			$subject[$key] = api_str_ireplace($search, $replace, $val, $count, $encoding);
 		}
 		return $subject;
 	}
-
 	if (is_array($search)) {
 		foreach (array_keys($search) as $key) {
 			if (is_array($replace)) {
@@ -466,30 +506,36 @@ function api_str_ireplace($search, $replace, $subject, & $count = null, $encodin
 		}
 		return $subject;
 	}
-
 	$search = api_strtolower($search, $encoding);
 	$subject_lower = api_strtolower($subject, $encoding);
-
 	$total_matched_strlen = 0;
 	$i = 0;
-
 	while (preg_match(api_add_pcre_unicode_modifier('/(.*?)'.preg_quote($search, '/').'/s', $encoding), $subject_lower, $matches)) {
 		$matched_strlen = api_strlen($matches[0], $encoding);
 		$subject_lower = api_substr($subject_lower, $matched_strlen, api_strlen($subject_lower, $encoding), $encoding);
-
 		$offset = $total_matched_strlen + api_strlen($matches[1], $encoding) + ($i * (api_strlen($replace, $encoding) - 1));
 		$subject = api_substr_replace($subject, $replace, $offset, api_strlen($search), $encoding);
-
 		$total_matched_strlen += $matched_strlen;
 		$i++;
 	}
-
 	$count += $i;
 	return $subject;
 }
 
-// This is a multibyte replacement of str_split().
-// See http://php.net/str_split
+/**
+ * Converts a string to an array.
+ * @param string $string		The input string.
+ * @param int $split_length		Maximum character-length of the chunk, one character by default.
+ * @param string $encoding		The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return array				The result array of chunks with the spcified length.
+ * Notes:
+ * If the optional split_length parameter is specified, the returned array will be broken down into chunks
+ * with each being split_length in length, otherwise each chunk will be one character in length.
+ * FALSE is returned if split_length is less than 1.
+ * If the split_length length exceeds the length of string, the entire string is returned as the first (and only) array element.
+ * This function is aimed at replacing the function str_split() for human-language strings.
+ * @link http://php.net/str_split
+ */
 function api_str_split($string, $split_length = 1, $encoding = null) {
 	if ($split_length < 1) {
 		return false;
@@ -497,9 +543,7 @@ function api_str_split($string, $split_length = 1, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
 	}
-
 	$result = array();
-
 	if (api_mb_supports($encoding)) {
 		for ($i = 0, $length = @mb_strlen($string, $encoding); $i < $length; $i += $split_length) {
 			$result[] = @mb_substr($string, $i, $split_length, $encoding);
@@ -514,21 +558,37 @@ function api_str_split($string, $split_length = 1, $encoding = null) {
 			$result[] = substr($string, $i, $split_length);
 		}
 	}
-
 	return $result;
 }
 
-// This is a multibyte replacement of strcasecmp().
-// See http://php.net/manual/en/function.strcasecmp
-function api_strcasecmp($str1, $str2, $encoding = null) {
+/**
+ * Case-insensitive string comparison wuth extended multibyte support.
+ * @param string $string1	The first string.
+ * @param string $string2	The second string.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return int				Returns < 0 if $string1 is less than $string2; > 0 if $string1 is greater than $string2; and 0 if the strings are equal. 
+ * This function is aimed at replacing the function strcasecmp() for human-language strings.
+ * @link http://php.net/manual/en/function.strcasecmp
+ */
+function api_strcasecmp($string1, $string2, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
 	}
-	return strcmp(api_strtolower($str1, $encoding), api_strtolower($str2, $encoding));
+	return strcmp(api_strtolower($string1, $encoding), api_strtolower($string2, $encoding));
 }
 
-// This is a multibyte replacement of stripos().
-// See http://php.net/manual/en/function.mb-stripos
+/**
+ * Finds position of first occurrence of a string within another, case insensitive.
+ * @param string $haystack	The string from which to get the position of the first occurrence.
+ * @param string $needle	The string to be found.
+ * @param int $offset		The position in $haystack to start searching from. If it is omitted, searching starts from the beginning.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return mixed			Return the numeric position of the first occurrence of $needle in the $haystack, or FALSE if $needle is not found.
+ * Note: The first character's position is 0, the second character position is 1, and so on. 
+ * This function is aimed at replacing the functions stripos() and mb_stripos() for human-language strings.
+ * @link http://php.net/manual/en/function.stripos
+ * @link http://php.net/manual/en/function.mb-stripos
+ */
 function api_stripos($haystack, $needle, $offset = 0, $encoding = null) {
 	if (empty($encoding)){
 		$encoding = api_mb_internal_encoding();
@@ -541,8 +601,20 @@ function api_stripos($haystack, $needle, $offset = 0, $encoding = null) {
 	return stripos($haystack, $needle, $offset);
 }
 
-// This is a multibyte replacement of stristr().
-// See http://php.net/manual/en/function.mb-stristr
+/**
+ * Finds first occurrence of a string within another, case insensitive.
+ * @param string $haystack	The string from which to get the first occurrence.
+ * @param string @needle	The string to be found.
+ * @param bool $part		Determines which portion of $haystack this function returns. The default value is FALSE.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return mixed			Returns the portion of $haystack, or FALSE if $needle is not found.
+ * Notes:
+ * If $part is set to TRUE, the function returns all of $haystack from the beginning to the first occurrence of $needle.
+ * If $part is set to FALSE, the function returns all of $haystack from the first occurrence of $needle to the end.
+ * This function is aimed at replacing the functions stristr() and mb_stristr() for human-language strings.
+ * @link http://php.net/manual/en/function.stristr
+ * @link http://php.net/manual/en/function.mb-stristr
+ */
 function api_stristr($haystack, $needle, $part = false, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -556,8 +628,15 @@ function api_stristr($haystack, $needle, $part = false, $encoding = null) {
 	return stristr($haystack, $needle, $part);
 }
 
-// Returns length of the input string.
-// See http://php.net/manual/en/function.mb-strlen
+/**
+ * Returns length of the input string.
+ * @param string $string	The string which length is to be calculated.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return int				Returns the number of characters within the string. A multi-byte character is counted as 1.
+ * This function is aimed at replacing the functions strlen() and mb_strlen() for human-language strings.
+ * @link http://php.net/manual/en/function.strlen
+ * @link http://php.net/manual/en/function.mb-strlen
+ */
 function api_strlen($string, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -571,8 +650,18 @@ function api_strlen($string, $encoding = null) {
 	return strlen($string);
 }
 
-// This is a multibyte replacement of strpos().
-// See http://php.net/manual/en/function.mb-strpos
+/**
+ * Finds position of first occurrence of a string within another.
+ * @param string $haystack	The string from which to get the position of the first occurrence.
+ * @param string $needle	The string to be found.
+ * @param int $offset		The position in $haystack to start searching from. If it is omitted, searching starts from the beginning.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return mixed			Return the numeric position of the first occurrence of $needle in the $haystack, or FALSE if $needle is not found.
+ * Note: The first character's position is 0, the second character position is 1, and so on. 
+ * This function is aimed at replacing the functions strpos() and mb_strpos() for human-language strings.
+ * @link http://php.net/manual/en/function.strpos
+ * @link http://php.net/manual/en/function.mb-strpos
+ */
 function api_strpos($haystack, $needle, $offset = 0, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -586,8 +675,20 @@ function api_strpos($haystack, $needle, $offset = 0, $encoding = null) {
 	return strpos($haystack, $needle, $offset);
 }
 
-// This is a multibyte replacement of strrchr().
-// See http://php.net/manual/en/function.mb-strrchr
+/**
+ * Finds the last occurrence of a character in a string.
+ * @param string $haystack	The string from which to get the last occurrence.
+ * @param string $needle	The string which first character is to be found.
+ * @param bool $part		Determines which portion of $haystack this function returns. The default value is FALSE.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return mixed			Returns the portion of $haystack, or FALSE if the first character from $needle is not found.
+ * Notes:
+ * If $part is set to TRUE, the function returns all of $haystack from the beginning to the first occurrence.
+ * If $part is set to FALSE, the function returns all of $haystack from the first occurrence to the end.
+ * This function is aimed at replacing the functions strrchr() and mb_strrchr() for human-language strings.
+ * @link http://php.net/manual/en/function.strrchr
+ * @link http://php.net/manual/en/function.mb-strrchr
+ */
 function api_strrchr($haystack, $needle, $part = false, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -601,8 +702,14 @@ function api_strrchr($haystack, $needle, $part = false, $encoding = null) {
 	return strrchr($haystack, $needle);
 }
 
-// This is a multibyte replacement of strrev().
-// See http://php.net/manual/en/function.strrev
+/**
+ * Reverses a string.
+ * @param string $string	The string to be reversed.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			Returns the reversed string.
+ * This function is aimed at replacing the function strrev() for human-language strings.
+ * @link http://php.net/manual/en/function.strrev
+ */
 function api_strrev($string, $encoding = null) {
 	if (empty($string)) {
 		return '';
@@ -617,8 +724,18 @@ function api_strrev($string, $encoding = null) {
 	return $result;
 }
 
-// This is a multibyte replacement of strrpos().
-// See http://php.net/manual/en/function.mb-strrpos
+/**
+ *  Finds the position of last occurrence of a string in a string.
+ * @param string $haystack	The string from which to get the position of the last occurrence.
+ * @param string $needle	The string to be found.
+ * @param int $offset		$offset may be specified to begin searching an arbitrary position. Negative values will stop searching at an arbitrary point prior to the end of the string.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return mixed			Return the numeric position of the first occurrence of $needle in the $haystack, or FALSE if $needle is not found.
+ * Note: The first character's position is 0, the second character position is 1, and so on. 
+ * This function is aimed at replacing the functions strrpos() and mb_strrpos() for human-language strings.
+ * @link http://php.net/manual/en/function.strrpos
+ * @link http://php.net/manual/en/function.mb-strrpos
+ */
 function api_strrpos($haystack, $needle, $offset = 0, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -632,8 +749,20 @@ function api_strrpos($haystack, $needle, $offset = 0, $encoding = null) {
 	return strrpos($haystack, $needle, $offset);
 }
 
-// This is a multibyte replacement of strstr().
-// See http://php.net/manual/en/function.mb-strstr
+/**
+ * Finds first occurrence of a string within another.
+ * @param string $haystack	The string from which to get the first occurrence.
+ * @param string @needle	The string to be found.
+ * @param bool $part		Determines which portion of $haystack this function returns. The default value is FALSE.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return mixed			Returns the portion of $haystack, or FALSE if $needle is not found.
+ * Notes:
+ * If $part is set to TRUE, the function returns all of $haystack from the beginning to the first occurrence of $needle.
+ * If $part is set to FALSE, the function returns all of $haystack from the first occurrence of $needle to the end.
+ * This function is aimed at replacing the functions strstr() and mb_strstr() for human-language strings.
+ * @link http://php.net/manual/en/function.strstr
+ * @link http://php.net/manual/en/function.mb-strstr
+ */
 function api_strstr($haystack, $needle, $part = false, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -647,8 +776,15 @@ function api_strstr($haystack, $needle, $part = false, $encoding = null) {
 	return strstr($haystack, $needle, $part);
 }
 
-// Makes a string lowercase.
-// See http://php.net/manual/en/function.mb-strtolower
+/**
+ * Makes a string lowercase.
+ * @param string $string	The string being lowercased.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			Returns the string with all alphabetic characters converted to lowercase.
+ * This function is aimed at replacing the functions strtolower() and mb_strtolower() for human-language strings.
+ * @link http://php.net/manual/en/function.strtolower
+ * @link http://php.net/manual/en/function.mb-strtolower
+ */
 function api_strtolower($string, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -662,8 +798,15 @@ function api_strtolower($string, $encoding = null) {
 	return strtolower($string);
 }
 
-// Makes a string uppercase.
-// See http://php.net/manual/en/function.mb-strtoupper
+/**
+ * Makes a string uppercase.
+ * @param string $string	The string being uppercased.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			Returns the string with all alphabetic characters converted to uppercase.
+ * This function is aimed at replacing the functions strtoupper() and mb_strtoupper() for human-language strings.
+ * @link http://php.net/manual/en/function.strtoupper
+ * @link http://php.net/manual/en/function.mb-strtoupper
+ */
 function api_strtoupper($string, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -677,10 +820,17 @@ function api_strtoupper($string, $encoding = null) {
 	return strtoupper($string);
 }
 
-// Translates certain characters.
-// See http://php.net/manual/en/function.strtr
-// TODO: To be revised and tested.
-// It would be good tihs function to be removed. I hesitate to do it right now.
+/**
+ * Translates certain characters.
+ * @param string $string	The string being translated.
+ * @param mixed $from		A string that contains the character to be replaced. This parameter can be also an array with pairs of characters 'from' => 'to'.
+ * @param string $to		A string that contains the replacing characters.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			This function returns a copy of $string, translating all occurrences of each character in $from to the corresponding character in $to.
+ * This function is aimed at replacing the function strtr() for human-language strings.
+ * @link http://php.net/manual/en/function.strtr
+ * TODO: To be revised and tested. Probably this function will be not needed.
+ */
 function api_strtr($string, $from, $to = null, $encoding = null) {
 	if (empty($string)) {
 		return '';
@@ -702,8 +852,8 @@ function api_strtr($string, $from, $to = null, $encoding = null) {
 			$encoding = api_mb_internal_encoding();
 		}
 		$translator = array();
-		$arr_from = api_get_characters($from, $encoding);
-		$arr_to = api_get_characters($to, $encoding);
+		$arr_from = api_str_split($from, 1, $encoding);
+		$arr_to = api_str_split($to, 1, $encoding);
 		$n = count($arr_from);
 		$n2 = count($arr_to);
 		if ($n > $n2) $n = $n2;
@@ -711,7 +861,7 @@ function api_strtr($string, $from, $to = null, $encoding = null) {
 			$translator[$arr_from[$i]] = $arr_to[$i];
 		}
 	}
-	$arr_string = api_get_characters($string, $encoding);
+	$arr_string = api_str_split($string, 1, $encoding);
 	$n = count($arr_string);
 	$result = '';
 	for ($i = 0; $i < $n; $i++) {
@@ -724,13 +874,23 @@ function api_strtr($string, $from, $to = null, $encoding = null) {
 	return $result;
 }
 
-// Performs a multi-byte safe substr() operation based on number of characters.
-// See http://bg.php.net/manual/en/function.mb-substr
+/**
+// Gets part of a string.
+ * @param string $string	The input string.
+ * @param int $start		The first position from which the extracted part begins.
+ * @param int $length		The length in character of the extracted part.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			Returns the part of the string specified by the start and length parameters.
+ * Note: First character's position is 0. Second character position is 1, and so on.
+ * This function is aimed at replacing the functions substr() and mb_substr() for human-language strings.
+ * @link http://php.net/manual/en/function.substr
+ * @link http://php.net/manual/en/function.mb-substr
+ */
 function api_substr($string, $start, $length = null, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
 	}
-	// Passing null as $length will mean 0. This behaviour have to be corrected.
+	// Passing null as $length would mean 0. This behaviour has been corrected here.
 	if (is_null($length)) {
 		$length = api_strlen($string, $encoding);
 	}
@@ -743,24 +903,25 @@ function api_substr($string, $start, $length = null, $encoding = null) {
 	return substr($string, $start, $length);
 }
 
-// Puts a suffix into a string.
-// The input variables could be arrays too.
-function api_suffix($string, $suffix) {
-	if (is_array($string)) {
-		if (is_array($suffix)) {
-			return array_map('api_suffix', $string, $suffix);
-		} else {
-			return array_map('api_suffix', $string, array_fill(0 , count($string) , $suffix));
-		}
-	}
-	if (is_array($suffix)) {
-		$suffix = implode('', $suffix);
-	}
-	return $string.$suffix;
-}
-
-// This is a multibyte replacement of substr_replace().
-// See http://php.net/manual/function.substr-replace
+/**
+ * Replaces text within a portion of a string.
+ * @param string $string		The input string.
+ * @param string $replacement	The replacement string.
+ * @param int $start			The position from which replacing will begin.
+ * Notes:
+ * If $start is positive, the replacing will begin at the $start'th offset into the string.
+ * If $start is negative, the replacing will begin at the $start'th character from the end of the string.
+ * @param int $length			The position where replacing will end.
+ * Notes:
+ * If given and is positive, it represents the length of the portion of the string which is to be replaced.
+ * If it is negative, it represents the number of characters from the end of string at which to stop replacing.
+ * If it is not given, then it will default to api_strlen($string); i.e. end the replacing at the end of string.
+ * If $length is zero, then this function will have the effect of inserting replacement into the string at the given start offset. 
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string				The result string is returned.
+ * This function is aimed at replacing the function substr_replace() for human-language strings.
+ * @link http://php.net/manual/function.substr-replace
+ */
 function api_substr_replace($string, $replacement, $start, $length = null, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -772,13 +933,19 @@ function api_substr_replace($string, $replacement, $start, $length = null, $enco
 			$length = api_strlen($string, $encoding) - $start + $length;
 		}
 		return
-			api_substr($string, 0, $start, $encoding) .$replacement .
+			api_substr($string, 0, $start, $encoding) . $replacement .
 			api_substr($string, $start + $length, api_strlen($string, $encoding), $encoding);
 	}
 }
 
-// Returns a string with the first character capitalized, if that character is alphabetic.
-// See http://php.net/manual/en/function.ucfirst
+/**
+ * Makes a string's first character uppercase.
+ * @param string $string	The input string.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			Returns a string with the first character capitalized, if that character is alphabetic.
+ * This function is aimed at replacing the function ucfirst() for human-language strings.
+ * @link http://php.net/manual/en/function.ucfirst
+ */
 function api_ucfirst($string, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -786,8 +953,14 @@ function api_ucfirst($string, $encoding = null) {
    	return api_strtoupper(api_substr($string, 0, 1, $encoding), $encoding) . api_substr($string, 1, api_strlen($string, $encoding), $encoding);
 }
 
-// Uppercases the first character of each word in a string.
-// See http://php.net/manual/en/function.ucwords
+/**
+ * Uppercases the first character of each word in a string.
+ * @param string $string	The input string.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			Returns the modified string.
+ * This function is aimed at replacing the function ucwords() for human-language strings.
+ * @link http://php.net/manual/en/function.ucwords
+ */
 function api_ucwords($string, $encoding = null) {
 	if (empty($encoding)) {
 		$encoding = api_mb_internal_encoding();
@@ -801,8 +974,12 @@ function api_ucwords($string, $encoding = null) {
 	return ucwords($string);
 }
 
-// This function adds a unicode modifier to a
-// Perl-compatible regular expression when it is necessary.
+/**
+ * This function adds a unicode modifier (u suffix) to a Perl-compatible regular expression depending on the specified encoding.
+ * @param string $pcre		The Perl-compatible regular expression.
+ * @param string $encoding	The used internally by this function character encoding. If it is omitted, the platform character set will be used by default.
+ * @return string			Returns the same regular expression wit a suffix 'u' if $encoding is 'UTF-8'.
+ */
 function api_add_pcre_unicode_modifier($pcre, $encoding = null) {
 	if (empty($encoding)){
 		$encoding = api_get_system_encoding();
@@ -810,18 +987,18 @@ function api_add_pcre_unicode_modifier($pcre, $encoding = null) {
 	return api_is_utf8($encoding) ? $pcre.'u' : $pcre;
 }
 
+/**
+ * ----------------------------------------------------------------------------
+ * Encoding management functions
+ * ----------------------------------------------------------------------------
+ */
 
-//----------------------------------------------------------------------------
-// Encoding management functions
-//----------------------------------------------------------------------------
-
-
-// Returns the most-probably used non-UTF-8 encoding for the given language.
-// The $language parameter must be cleaned by api_refine_language_id() if it
-// is necessary.
-// If the returned value is not as you expect, you may do the following:
-// In the table $encodings below, correct the order of the encodings for your
-// language, or if it is necessary - insert at the first place a new encoding.
+/**
+ * Returns the most-probably used non-UTF-8 encoding for the given language.
+ * @param string $language	The specified language, the default value is the language of the user interface.
+ * Note: The $language parameter must be cleaned by api_refine_language_id() if it is necessary.
+ * @return string			The correspondent encoding to the specified language.
+ */
 function api_get_non_utf8_encoding($language = null) {
 	if (empty($language)) {
 		$language = api_refine_language_id(api_get_interface_language());
@@ -838,7 +1015,11 @@ function api_get_non_utf8_encoding($language = null) {
 	}
 }
 
-// Returns a two-dimensional array of non-UTF-8 encodings for all system languages.
+/**
+ * Returns a table with non-UTF-8 encodings for all system languages.
+ * @return array		Returns an array in the form array('language1' => array('encoding1', encoding2', ...), ...)
+ * Note: The function api_get_non_utf8_encoding() returns the first encoding from this array that is correspondent to the given language. 
+ */
 function & api_non_utf8_encodings() {
 	// The following list may have some inconsistencies.
 	// Place the most used for your language encoding at the first place.
@@ -904,26 +1085,44 @@ vietnamese: WINDOWS-1258;
 	return $encodings;
 }
 
-// This function unifies internally the encoding identificators.
-// It is to be adjusted in case of id comparison problems.
+/**
+ * This function unifies the encoding identificators, so they could be compared.
+ * @param string $encoding	The specified encoding.
+ * @return string			Returns the encoding identificator modified in suitable for comparison way.
+ */
 function api_refine_encoding_id($encoding) {
 	return strtoupper($encoding);
 }
 
-// This function checks whether two $encoding are equal (same, equvalent).
-function api_equal_encodings($encoding_1, $encoding_2) {
+/**
+ * This function checks whether two $encoding are equal (same, equvalent).
+ * @param string $encoding1		The first encoding
+ * @param string $encoding2		The second encoding
+ * @return bool					Returns TRUE if the encodings are equal, FALSE otherwise.
+ */
+function api_equal_encodings($encoding1, $encoding2) {
 	// We have to deal with aliases. This function alone does not solve
 	// the problem entirely. And there is no time for this kind of research.
 	// At the momemnt, the quick proposition could be:
-	return strcmp(api_refine_encoding_id($encoding_1), api_refine_encoding_id($encoding_2)) == 0 ? true : false;
+	return strcmp(api_refine_encoding_id($encoding1), api_refine_encoding_id($encoding2)) == 0 ? true : false;
 }
 
-// Returns true if the given encoding id means UTF-8, otherwise returns false.
+/**
+ * This function checks whether a given encoding is UTF-8.
+ * @param string $encoding		The tested encoding.
+ * @return bool					Returns TRUE if the given encoding id means UTF-8, otherwise returns false.
+ */
 function api_is_utf8($encoding) {
 	return api_equal_encodings($encoding, 'UTF-8');
 }
 
-// Returns the encoding currently used by the system.
+/**
+ * This function returns the encoding, currently used by the system.
+ * @return string	The system's encoding.
+ * Note: The value of api_get_setting('platform_charset') is tried to be returned first,
+ * on the second place the global variable $charset is tried to be returned. If for some
+ * reason both attempts fail, 'ISO-8859-15' will be returned.
+ */
 function api_get_system_encoding() {
 	$system_encoding = api_get_setting('platform_charset');
 	if (!empty($system_encoding)) {
@@ -933,8 +1132,13 @@ function api_get_system_encoding() {
 	return empty($charset) ? 'ISO-8859-15' : $charset;
 }
 
-// Sets/Gets internal character encoding.
-// See http://php.net/manual/en/function.mb-internal-encoding
+/**
+ * Sets/Gets internal character encoding of the common string functions within the PHP mbstring extension.
+ * @param string $encoding	When this parameter is given, the function sets the internal encoding.
+ * @return string			When $encoding parameter is not given, the function returns the internal encoding.
+ * Note: This function is used in the global initialization script for setting the internal encoding to the platform's character set.
+ * @link http://php.net/manual/en/function.mb-internal-encoding
+ */
 function api_mb_internal_encoding($encoding = null) {
 	static $mb_internal_encoding = null;
 	if (empty($encoding)) {
@@ -950,8 +1154,13 @@ function api_mb_internal_encoding($encoding = null) {
 	return false;
 }
 
-// Sets/Gets current encoding for multibyte regex.
-// See http://php.net/manual/en/function.mb-regex-encoding
+/**
+ * Sets/Gets internal character encoding of the regular expression functions (ereg-like) within the PHP mbstring extension.
+ * @param string $encoding	When this parameter is given, the function sets the internal encoding.
+ * @return string			When $encoding parameter is not given, the function returns the internal encoding.
+ * Note: This function is used in the global initialization script for setting the internal encoding to the platform's character set.
+ * @link http://php.net/manual/en/function.mb-regex-encoding
+ */
 function api_mb_regex_encoding($encoding = null) {
 	static $mb_regex_encoding = null;
 	if (empty($encoding)) {
@@ -967,13 +1176,24 @@ function api_mb_regex_encoding($encoding = null) {
 	return false;
 }
 
-// Retrieves internal configuration variables of iconv extension.
-// The parameter $type could be: 'iconv_internal_encoding', 'iconv_input_encoding', or 'iconv_output_encoding'.
-// See http://php.net/manual/en/function.iconv-get-encoding
+/**
+ * Retrieves specified internal encoding configuration variable within the PHP iconv extension.
+ * @param string $type	The parameter $type could be: 'iconv_internal_encoding', 'iconv_input_encoding', or 'iconv_output_encoding'.
+ * @return mixed		The function returns the requested encoding or FALSE on error.
+ * @link http://php.net/manual/en/function.iconv-get-encoding
+ */
 function api_iconv_get_encoding($type) {
 	return api_iconv_set_encoding($type);
 }
 
+/**
+ * Sets specified internal encoding configuration variables within the PHP iconv extension.
+ * @param string $type		The parameter $type could be: 'iconv_internal_encoding', 'iconv_input_encoding', or 'iconv_output_encoding'.
+ * @param string $encoding	The desired encoding to be set.
+ * @return bool				Returns TRUE on success, FALSE on error.
+ * Note: This function is used in the global initialization script for setting these three internal encodings to the platform's character set.
+ * @link http://php.net/manual/en/function.iconv-set-encoding
+ */
 // Sets current setting for character encoding conversion.
 // The parameter $type could be: 'iconv_internal_encoding', 'iconv_input_encoding', or 'iconv_output_encoding'.
 function api_iconv_set_encoding($type, $encoding = null) {
@@ -983,7 +1203,6 @@ function api_iconv_set_encoding($type, $encoding = null) {
 	if (!api_iconv_present()) {
 		return false;
 	}
-
 	switch ($type) {
 		case 'iconv_internal_encoding':
 			if (empty($encoding)) {
@@ -1003,7 +1222,6 @@ function api_iconv_set_encoding($type, $encoding = null) {
 				return false;
 			}
 			break;
-
 		case 'iconv_input_encoding':
 			if (empty($encoding)) {
 				if (is_null($iconv_input_encoding)) {
@@ -1022,7 +1240,6 @@ function api_iconv_set_encoding($type, $encoding = null) {
 				return false;
 			}
 			break;
-
 		case 'iconv_output_encoding':
 			if (empty($encoding)) {
 				if (is_null($iconv_output_encoding)) {
@@ -1041,18 +1258,25 @@ function api_iconv_set_encoding($type, $encoding = null) {
 				return false;
 			}
 			break;
-
 		default:
 			return false;
 	}
 }
 
-// Checks whether the specified encoding is supported by this API.
+/**
+ * Checks whether a specified encoding is supported by this API.
+ * @param string $encoding	The specified encoding.
+ * @return bool				Returns TRUE when the specified encoding is supported, FALSE othewise.
+ */
 function api_is_encoding_supported($encoding) {
 	return api_mb_supports($encoding) || api_iconv_supports($encoding);
 }
 
-// Checks whether the specified encoding is supported by mbstring library.
+/**
+ * Checks whether the specified encoding is supported by the PHP mbstring extension.
+ * @param string $encoding	The specified encoding.
+ * @return bool				Returns TRUE when the specified encoding is supported, FALSE othewise.
+ */
 function api_mb_supports($encoding) {
 	static $supported = array();
 	$encoding = api_refine_encoding_id($encoding);
@@ -1064,7 +1288,11 @@ function api_mb_supports($encoding) {
 	return $supported[$encoding] ? true : false;
 }
 
-// Checks whether the specified non-UTF-8 encoding is supported by iconv library.
+/**
+ * Checks whether the specified encoding is supported by the PHP iconv extension.
+ * @param string $encoding	The specified encoding.
+ * @return bool				Returns TRUE when the specified encoding is supported, FALSE othewise.
+ */
 function api_iconv_supports($encoding) {
 	static $supported = array();
 	$encoding = api_refine_encoding_id($encoding);
@@ -1083,7 +1311,10 @@ function api_iconv_supports($encoding) {
 	return $supported[$encoding];
 }
 
-// Checks whether the iconv library is installed and works.
+/**
+ * Checks whether the PHP iconv extension is installed and it works.
+ * @return bool				Returns TRUE when the iconv extension is detected, FALSE othewise.
+ */
 function api_iconv_present() {
 	static $iconv_present = null;
 	if (!is_null($iconv_present)) {
@@ -1100,7 +1331,11 @@ function api_iconv_present() {
 	return $iconv_present;
 }
 
-// Checks whether the specified encoding is supported by html-entities operations.
+/**
+ * Checks whether the specified encoding is supported by the html-entitiy related functions.
+ * @param string $encoding	The specified encoding.
+ * @return bool				Returns TRUE when the specified encoding is supported, FALSE othewise.
+ */
 function api_html_entity_supports($encoding) {
 	static $supported = array();
 	$encoding = api_refine_encoding_id($encoding);
@@ -1128,13 +1363,18 @@ EUC-JP, EUCJP
 	return $supported[$encoding] ? true : false;
 }
 
+/**
+ * ----------------------------------------------------------------------------
+ * String validation functions concerning some encodings
+ * ----------------------------------------------------------------------------
+ */
 
-//----------------------------------------------------------------------------
-// String validation functions concerning some encodings
-//----------------------------------------------------------------------------
-
-
-// Returns true if the specified string is a valid UTF-8 one and false otherwise.
+/**
+ * Checks a string for UTF-8 validity.
+ * @param string $string	The string to be tested/validated.
+ * @return bool				Returns TRUE when the tested string is valid UTF-8 one, FALSE othewise.
+ * @link http://en.wikipedia.org/wiki/UTF-8
+ */
 function api_is_valid_utf8($string) {
 
 	//return @mb_detect_encoding($string, 'UTF-8', true) == 'UTF-8' ? true : false;
@@ -1142,8 +1382,7 @@ function api_is_valid_utf8($string) {
 	// found a string with a single cyrillic letter (single byte), that is
 	// wrongly detected as UTF-8. Possibly, there would be problems with other
 	// languages too.
-	//
-	// To understand the following algorithm see http://en.wikipedia.org/wiki/UTF-8
+	// An alternative implementation will be used:
 
 	$len = strlen($string);
 	$i = 0;
@@ -1324,19 +1563,26 @@ function api_is_valid_utf8($string) {
 	return true;							// Empty strings are valid too.
 }
 
-// Checks whether a string contains 7bit ASCII characters only.
+/**
+ * Checks whether a string contains 7-bit ASCII characters only.
+ * @param string $string	The string to be tested/validated.
+ * @return bool				Returns TRUE when the tested string contains 7-bit ASCII characters only, FALSE othewise.
+ */
 function api_is_valid_ascii($string) {
 	return @mb_detect_encoding($string, 'ASCII', true) == 'ASCII' ? true : false;
 }
 
+/**
+ * ----------------------------------------------------------------------------
+ * Language management functions
+ * ----------------------------------------------------------------------------
+ */
 
-//----------------------------------------------------------------------------
-// Language management functions
-//----------------------------------------------------------------------------
-
-
-// Returns a pure language id, without possible suffixes
-// that will disturb language identification in certain cases.
+/**
+ * Returns a purified language id, without possible suffixes that will disturb language identification in certain cases.
+ * @param string $language	The input language identificator, for example 'french_unicode'.
+ * @param string			The same purified or filtered language identificator, for example 'french'.
+ */
 function api_refine_language_id($language) {
 	return (
 		str_replace('_unicode', '', strtolower(
@@ -1346,14 +1592,20 @@ function api_refine_language_id($language) {
 		str_replace('_KM', '', $language)))))));
 }
 
+/**
+ * ----------------------------------------------------------------------------
+ * Array functions
+ * ----------------------------------------------------------------------------
+ */
 
-//----------------------------------------------------------------------------
-// Array functions
-//----------------------------------------------------------------------------
-
-
-// A case insensitive version of in_array() function.
-// See http://php.net/manual/en/function.in-array.php
+/**
+ * Checks if a value exists in an array, a case insensitive version of in_array() function with extended multibyte support.
+ * @param mixed $needle		The searched value. If needle is a string, the comparison is done in a case-insensitive manner.
+ * @param array $haystack	The array.
+ * @param bool $strict		If is set to TRUE then the function will also check the types of the $needle in the $haystack. The default value if FALSE.
+ * @return bool				Returns TRUE if $needle is found in the array, FALSE otherwise.
+ * @link http://php.net/manual/en/function.in-array.php
+ */
 function api_in_array_nocase($needle, $haystack, $strict = false, $encoding = null) {
 	if (is_array($needle)) {
 		foreach ($needle as $item) {
@@ -1361,7 +1613,6 @@ function api_in_array_nocase($needle, $haystack, $strict = false, $encoding = nu
 		}
 		return false;
 	}
-
 	if (!is_string($needle)) {
 		return in_array($needle, $haystack, $strict);
 	}
@@ -1465,4 +1716,4 @@ if (!function_exists('mb_strstr')) {
 	}
 }
 
-?>
+?>
\ No newline at end of file