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Detailed explanation of how to prevent hotlinking in PHP

小云云Original: 2018-02-01 13:01:472989browse

This article mainly introduces the method of anti-hotlinking in PHP, and analyzes the related technologies and specific implementation techniques involved in anti-hotlinking in PHP in the form of examples. Friends who need it can refer to it. I hope it can help everyone.

$_SERVER['HTTP_REFERER'] acquisition situation

Note $_SERVER['HTTP_REFERER'] may not always be obtained. It can only be obtained under the following circumstances:

1. The circumstances under which HTTP_REFERER can be obtained are as follows:

1. Use cfba799dd43fce78ec3e9e3d200b7e48
2 directly. Form submitted with Submit or 764a0a970dbc75966e734f5ea597d024 (POST or GET)
3． Form submitted using Jscript (POST or GET)

2. The following situations cannot be obtained:

1. Link from Favorites
2. Click "Home" or the customized address
3. Use Jscript's location.href or location.replace()
4． Directly enter the address
5 in the browser. c37f721670919360921ccb8afc9eb479
6． 707ab8d2056c6e1f516d2bf3c9988ff9 or d2eacb9d552db150e90498bcd18784f7Go to
7． Use XML to load the address

strrpos Function explanation:

strrpos - Calculate the position of the last occurrence of the specified string in the target string

Description

int strrpos (string $haystack, string $needle [, int $offset = 0])<br>Returns the last occurrence of needle in string $haystack Numeric location.

$haystack	Find in this string.
$needle	If needle is not a string, it will be converted to an integer and treated as a sequential value of characters.

Return value

Returns the position where needle exists. If not found, returns FALSE.

Hot link judgment code: asd.php

<?php
//防盗链技术
//先判断是否获取到 $_SERVER[&#39;HTTP_REFERER&#39;] 变量
if(isset($_SERVER[&#39;HTTP_REFERER&#39;])){
  //判断$_SERVER[&#39;HTTP_REFERER&#39;]是不是以http://localhost/开始的
  if(strpos($_SERVER[&#39;HTTP_REFERER&#39;],"http://localhost")==0){
    echo &#39;<img src="a.png"/>&#39;;
  }
  else{
    header("Location:warning.php");//跳转页面到warning.php
    //echo $_SERVER["HTTP_REFERER"];
  }
}
else {
  header("Location:warning.php");
}
?>

warning.php

<html>
<b>倒链</b>
</html>

Anti-theft Chain verification code

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<a href="http://localhost/wml/asd.php" rel="external nofollow" >验证防盗链</a>
</body>
</html>

The above is the understanding principle

Generally prevent hot links by configuring the server, such as nginx configuration access

( gif|jpg|jpeg|png|bmp|swf) White list of other files

Detailed configuration can be searched on Baidu

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php Crack anti-hotlinking

Detailed explanation of anti-hotlinking method in PHP

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