Check URL for valid format by pattern - php

Question

I have social bookmarking website and in this website users can submit link from others website (using booklet or bookmark button in bookmark bar, or by adding URLs in direct method).
The users have problem with some URLs when they add links with bookmark button in their browsers. The problem occurs with URLs that contain "&" character. Most of the users who work with Safari on Mac or Windows can not add such link with bookmark button.
Issue is that all URLs with "&" end up with $isLink = preg_match($pattern, $url); // Returns false (see the code below).
I removed part of my code (see comments in the snippet), and that fixed the problem.
But I do not want to remove this code. How can I fix the problem without removing it?
$url = htmlspecialchars(sanitize($_POST['url'], 3));
$url = str_replace('&', '&', $url);
$url = html_entity_decode($url);
if (strpos($url,'http')!==0) {
$url = "http://$url";
}
// check if URL is valid format
$pattern = '/^(([\w]+:)?\/\/)?(([\d\w]|%[a-fA-f\d]{2,2})+(:([\d\w]|%[a-fA-f\d]{2,2})+)?#)?([\d\w]([-\d\w]{0,253}[\d\w])?\.)+[\w]{2,4}(:[\d]+)?(\/([-+_~.,\d\w]|%[a-fA-f\d]{2,2})*)*(\?(&?([-+_~.,\d\w]|%[a-fA-f\d]{2,2})=?)*)?(#([-+_~.,\/\d\w]|%[a-fA-f\d]{2,2})*)?$/';
// vvv I REMOVED FROM HERE vvv
$isLink = preg_match($pattern, $url); // Returns true if a link
// ^^^ UNTIL HERE ^^^
if($url == "http://" || $url == "") {
if(Submit_Require_A_URL == false) {
$linkres->valid = true;
} else {
$linkres->valid = false;
}
$linkres->url_title = "";
} elseif ($isLink == false) {
$linkres->valid = false;
}
Website bookmark button code is:
javascript:q=(document.location.href);void(open('http://website.com/submit.php?url='+escape(q),'_self','resizable,location,menubar,toolbar,scrollbars,status'));

Answer 1

Why are you not using the PHP function "filter_var()" to check the url:
$url = $_POST['url'];
$isLink = filter_var($url, FILTER_VALIDATE_URL);