php if page url contains code example

Example 1: php if url contains

if(strpos($_SERVER['REQUEST_URI'], "string")) {
  ...
}

Example 2: php check if string contains url

preg_match('/(http|ftp|mailto)/', $string, $matches);
var_dump($matches);

Example 3: if browser url is having domain in it check using php

$url = 'http://' . $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];

if (!strpos($url,'mysql')) {
echo 'No mysql.'; //swapped with other echo statement
} else {
echo 'Mysql exists.';
}