Extract links from source page or subject

extract_links.php

<?php

/**
 * A function to extract links from source
 * @version     1.0
 * @author      Mohammed Al Ashaal
 * @copyright   2014
 * @license     New BSD License
 */
if ( ! function_exists('extract_links') ):

    /** Links must have schema */
    define('LINKS_MUST_SCHEMA', 2);

    /** links must hace path */
    define('LINKS_MUST_PATH', 4);

    /**
     * Extract links from a source page
     * @param   string  $source
     * @param   integer $flags
     * @return  array
     */
    function extract_links($source, $flags = 0)
    {
        $pattern = "((www\.|)([\p{N}\p{L}]+)\.[\p{N}\p{L}\.]+)";

        if ( LINKS_MUST_SCHEMA & $flags )
            $pattern = "([a-z]+:\/\/)" . $pattern;
        else
            $pattern = "([a-z]+:\/\/|)" . $pattern;

        if ( LINKS_MUST_PATH & $flags )
            $pattern = $pattern . "((\/)(\S*))";
        else
            $pattern = $pattern . "((\/|)(\S*))";
            
        if ( preg_match_all("/({$pattern})/ui", $source, $x) )
            return $x[1];
        else
            return array();
    }

endif;