Download .crx Chrome Extension file with PHP

crx-downloader.php

<?php
if(isset($_POST["submit"])){
	if(isset($_POST["url"]) && filter_var($_POST["url"], FILTER_VALIDATE_URL)){
		//Get extension id
		$pos = strrpos($_POST["url"], '/');
		$end = $pos === false ? $_POST["url"] : substr($_POST["url"], $pos + 1);
		$id = substr($end, 0, strpos($end, "?"));
		$durl = "https://clients2.google.com/service/update2/crx?response=redirect&x=id%3D".$id."%26uc&prodversion=32";
		//Simply get!
		header("Location: $durl");
		exit;

	}
}
?>
<form method="post">
	<input type="text" name="url">
	<input type="submit" name="submit" value="Download crx!">
</form>