<!DOCTYPE html>
<html>
<body>
<?php
$search = preg_quote("://", "/");
$input = 'https://www.w3school.com.cn/';
$pattern = "/$search/";
if(preg_match($pattern, $input)) {
echo "输入是一个 URL。";
} else {
echo "输入不是一个 URL。";
}
?>
</body>
</html>