Function analysis on php cracking anti-hotlink pictures

This article mainly introduces the function analysis of PHP cracking anti-hotlink images. It has a certain reference value. Now I share it with you. Friends in need can refer to it.

Only supports jpg and gif. Everyone. It can be modified to support multiple image formats

<?php 
$url=$_GET[&#39;url&#39;]; 
$ext=pathinfo($url,PATHINFO_EXTENSION); 
if($ext!=&#39;jpg&#39; && $ext!=&#39;gif&#39;){ // 只支持jpg和gif 
readfile(&#39;/upload/20081209130557536.gif&#39;); 
exit; 
} 
$file=md5($url).&#39;.&#39;.$ext; 
if(file_exists($file)){ 
readfile($file); 
exit; 
}else{ 
$data=file_get_contents($url); 
if(!$data){ // 读取失败 
readfile(&#39;/upload/20081209130557536.gif&#39;); 
exit; 
} 
$handle=fopen($file,&#39;wb&#39;); 
fwrite($handle,$data); 
fclose($handle); 
echo $data; 
} 
?>

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