Question

I want to use this regex for validating my urls in php with preg_match function but when i use it it says “Unknown modifier ‘&'”
what is the problem ?

$urlregex = "/^(http|ftp|https)\:\/\/";

        // USER AND PASS (optional)
        $urlregex .= "([a-z0-9+!*(),;?&=\$_.-]+(\:[a-z0-9+!*(),;?&=\$_.-]+)?@)?";

        // HOSTNAME OR IP
        $urlregex .= "[a-z0-9+\$_-]+(\.[a-z0-9+\$_-]+)+"; // http://x.x = minimum

        // PORT (optional)
        $urlregex .= "(\:[0-9]{2,5})?";
        // PATH (optional)
        $urlregex .= "(\/([a-z0-9+\$_-]\.?)+)*\/?";
        // GET Query (optional)
        $urlregex .= "(\?[a-z+&\$_.-][a-z0-9;:@/&%=+\$_.-]*)?";
        // ANCHOR (optional)
        $urlregex .= "(#[a-z_.-][a-z0-9+\$_.-]*)?\$/";
        if(preg_match($urlregex, $url) === 1)
        {
            $errors[] = "URL_ISNOTVALID";
            $ok =  false;
        }

Answer 1

Looks like you forgot to escape a forward slash:

$urlregex .= "(\?[a-z+&\$_.-][a-z0-9;:@/&%=+\$_.-]*)?";

should be

$urlregex .= "(\?[a-z+&\$_.-][a-z0-9;:@\/&%=+\$_.-]*)?";