PHP 5种方式获取文件后缀名

<?php
header("content-type:text/html;charset=utf-8");
  function get_ext1($filename) 
{ 
        return strrchr($filename,‘.‘); 
} 
 
function get_ext2($filename){ 
        return substr($filename,strrpos($filename,‘.‘)+1); 
} 
 
function get_ext3($filename){ 
        return array_pop(explode(‘.‘,$filename)); 
} 
 
function get_ext4($filename){ 
        return pathinfo($filename,PATHINFO_EXTENSION); 
} 
 
function get_ext5($filename){ 
        return strrev(substr(strrev($filename),0,strpos(strrev($filename),‘.‘))); 
} 
 
$filename = "qqq.php"; 

echo get_ext1($filename)."<br/>"; 
echo get_ext2($filename)."<br/>"; 
echo get_ext3($filename)."<br/>"; 
echo get_ext4($filename)."<br/>"; 
echo get_ext5($filename)."<br/>"; 


 ?>