chamilo-lms/main/inc/lib/formvalidator/Rule/Url.php

<?php

/**
 * Abstract base class for QuickForm validation rules
 */
require_once 'HTML/QuickForm/Rule.php';

/**
 * Validate urls
 *
 */
class HTML_QuickForm_Rule_Url extends HTML_QuickForm_Rule
{

    /**
     * Validates url
     *
     * @param string $url    
     * @return boolean  Returns true if valid, false otherwise.
     */
    function validate($url)
    {
        return (bool) filter_var($url, FILTER_VALIDATE_URL);
    }

}