php 获取文件扩展名的函数

<?php 
$file = "/home/lvyaozu/backup_20080115.txt"; 

for($i=1; $i < 6; $i++) { 
$func = &#39;get_file_ext_&#39; . $i; 
var_dump($func($file)); 
} 


function get_file_ext_1($file) { 
return strtolower(trim(substr(strrchr($file, &#39;.&#39;), 1))); 
} 

function get_file_ext_2($file) { 
return strtolower(trim(pathinfo($file, PATHINFO_EXTENSION))); 
} 

function get_file_ext_3($file) { 
return strtolower(trim(substr($file, strrpos($file, &#39;.&#39;)+1))); 
} 

function get_file_ext_4($file) { 
return strtolower(trim(array_pop(explode(&#39;.&#39;, $file)))); 
} 

function get_file_ext_5($file) { 
$tok = strtok($file, &#39;.&#39;); 
while($tok !== false) { 
$return = $tok; 
$tok = strtok(&#39;.&#39;); 
} 
return strtolower(trim($return)); 
} 
?>