diff --git a/main/inc/lib/system_announcements.lib.php b/main/inc/lib/system_announcements.lib.php
index ec40a0eb2f..248b4718b8 100755
--- a/main/inc/lib/system_announcements.lib.php
+++ b/main/inc/lib/system_announcements.lib.php
@@ -229,6 +229,7 @@ class SystemAnnouncementManager
 	 * @param int    Whether the announcement should be visible to anonymous users (1) or not (0)
 	 * @param string The language for which the announvement should be shown. Leave null for all langages
 	 * @param int    Whether to send an e-mail to all users (1) or not (0)
+	 * @return bool  True on success, false on failure
 	 */
 	public static function add_announcement($title, $content, $date_start, $date_end, $visible_teacher = 0, $visible_student = 0, $visible_guest = 0, $lang = null, $send_mail=0)
 	{
@@ -271,7 +272,12 @@ class SystemAnnouncementManager
 		if ($send_mail==1) {
 			SystemAnnouncementManager::send_system_announcement_by_email($title, $content,$visible_teacher, $visible_student);
 		}
-		return Database::query($sql);
+		$res = Database::query($sql);
+		if ($res === false) {
+			Debug::log_s(mysql_error());
+			return false
+		}
+		return true;
 	}
 	/**
 	 * Updates an announcement to the database
@@ -280,6 +286,7 @@ class SystemAnnouncementManager
 	 * @param string  $content : content of the announcement
 	 * @param array $date_start: start date of announcement (0 => day ; 1 => month ; 2 => year ; 3 => hour ; 4 => minute)
 	 * @param array $date_end : end date of announcement (0 => day ; 1 => month ; 2 => year ; 3 => hour ; 4 => minute)
+	 * @return	bool	True on success, false on failure
 	 */
 	public static function update_announcement($id, $title, $content, $date_start, $date_end, $visible_teacher = 0, $visible_student = 0, $visible_guest = 0,$lang=null, $send_mail=0)
 	{
@@ -322,18 +329,28 @@ class SystemAnnouncementManager
 		if ($send_mail==1) {
 			SystemAnnouncementManager::send_system_announcement_by_email($title, $content,$visible_teacher, $visible_student);
 		}
-		return Database::query($sql);
+		$res = Database::query($sql);
+		if ($res === false) {
+			Debug::log_s(mysql_error());
+			return false
+		}
+		return true;
 	}
 	/**
 	 * Deletes an announcement
 	 * @param 	int $id The identifier of the announcement that should be
-	 * @return	resource
+	 * @return	bool	True on success, false on failure
 	 */
 	public static function delete_announcement($id) {
 		$db_table = Database :: get_main_table(TABLE_MAIN_SYSTEM_ANNOUNCEMENTS);
 		$id = intval($id);
 		$sql = "DELETE FROM ".$db_table." WHERE id='".$id."'";
-		return Database::query($sql);
+		$res = Database::query($sql);
+		if ($res === false) {
+			Debug::log_s(mysql_error());
+			return false
+		}
+		return true;
 	}
 	/**
 	 * Gets an announcement
@@ -351,7 +368,7 @@ class SystemAnnouncementManager
 	 * Change the visibility of an announcement
 	 * @param 	int $announcement_id
 	 * @param 	int $user For who should the visibility be changed (possible values are VISIBLE_TEACHER, VISIBLE_STUDENT, VISIBLE_GUEST)
-	 * @return 	resource
+	 * @return 	bool	True on success, false on failure
 	 */
 	public static function set_visibility($announcement_id, $user, $visible) {
 		$db_table 			= Database::get_main_table(TABLE_MAIN_SYSTEM_ANNOUNCEMENTS);
@@ -360,9 +377,21 @@ class SystemAnnouncementManager
 
 		$field = ($user == VISIBLE_TEACHER ? 'visible_teacher' : ($user == VISIBLE_STUDENT ? 'visible_student' : 'visible_guest'));
 		$sql = "UPDATE ".$db_table." SET ".$field." = '".$visible."' WHERE id='".$announcement_id."'";
-		return Database::query($sql);
+		$res = Database::query($sql);
+		if ($res === false) {
+			Debug::log_s(mysql_error());
+			return false
+		}
+		return true;
 	}
 
+	/**
+	 * Send a system announcement by e-mail to all teachers/students depending on parameters
+	 * @param	string	Title
+	 * @param	string	Content
+	 * @param	int		Whether to send to all teachers (1) or not (0)
+	 * @param	int		Whether to send to all students (1) or not (0)
+	 */
 	public static function send_system_announcement_by_email($title, $content, $teacher, $student) {
 		global $_user;
 		global $_setting;
@@ -382,8 +411,11 @@ class SystemAnnouncementManager
 			return true;
 		}
 		$result = Database::query($sql);
+		if ($result === false) {
+			return false;
+		}
 		while($row = Database::fetch_array($result,'ASSOC')) {
-			@api_mail_html(api_get_person_name($row['firstname'], $row['lastname'], null, PERSON_NAME_EMAIL_ADDRESS), $row['email'], api_html_entity_decode(stripslashes($title), ENT_QUOTES, $charset), api_html_entity_decode(stripslashes(str_replace(array('\r\n', '\n', '\r'),'',$content)), ENT_QUOTES, $charset), api_get_person_name(api_get_setting('administratorName'), api_get_setting('administratorSurname'), null, PERSON_NAME_EMAIL_ADDRESS), api_get_setting('emailAdministrator'));
+			$res = @api_mail_html(api_get_person_name($row['firstname'], $row['lastname'], null, PERSON_NAME_EMAIL_ADDRESS), $row['email'], api_html_entity_decode(stripslashes($title), ENT_QUOTES, $charset), api_html_entity_decode(stripslashes(str_replace(array('\r\n', '\n', '\r'),'',$content)), ENT_QUOTES, $charset), api_get_person_name(api_get_setting('administratorName'), api_get_setting('administratorSurname'), null, PERSON_NAME_EMAIL_ADDRESS), api_get_setting('emailAdministrator'));
 		}
 	}
 }