SE'; // SET SOME DOMAIN EXTENSIONS $extension_array = array('com', 'net', 'org', 'biz'); // CHECK TO SEE IF OUR REGEX IS WORKING ... PRINT OUT ALL OF THE MATCHES if (preg_match_all('~(?:(?:http(?:s)?://)?(?:www\.)?[-A-Z0-9.]+(?:\.'.implode('|', $extension_array).')[-A-Z0-9_./]?(?:[-A-Z0-9#?/]+)?)~ims', $urls_as_string, $m)) { print_r($m); } // USE PREG_REPLACE_CALLBACK TO FORMAT THE URLS $content = preg_replace_callback( '~(?:(?:http(?:s)?://)?(?:www\.)?[-A-Z0-9.]+(?:\.'.implode('|', $extension_array).')[-A-Z0-9_./]?(?:[-A-Z0-9#?/]+)?)~ims', 'my_callback', $urls_as_string); // PRINT OUT THE FINISHED STRING print "\n\n\n\nFINAL OUTPUT: \n".$content; // THIS FUNCTION DOES A CRAPTASTIC JOB AT FORMATTING URLS function my_callback($m) { $url = $m[0]; $url_formatted = $url; if (!preg_match('~^http(s)?://~', $url)) { $url_formatted = 'http://'.$url; } $url_formatted = ''.$url.''; return $url_formatted; }