parse_url($url);pathinfo($path['path'],PATHINFO_EXTENSION);

<?php
    /** by www.phpddt.com */
    $url = "http://www.phpddt.com/abc/de/fg.php?id=1";
var_dump($url);
echo  '<hr>';
    $path = parse_url($url);
var_dump($path);
echo  '<hr>';
    echo  $path['path'];
    echo  '<hr>';
    echo pathinfo($path['path'],PATHINFO_EXTENSION);  //php

?>

string 'http://www.phpddt.com/abc/de/fg.php?id=1' (length=40)

---

array  'scheme' => string 'http' (length=4)  'host' => string 'www.phpddt.com' (length=14)  'path' => string '/abc/de/fg.php' (length=14)  'query' => string 'id=1' (length=4)

---

/abc/de/fg.php

---

php