Anti-crawler processing methods and strategies for PHP crawlers

PHP crawler anti-crawler processing methods and strategies

With the development of the Internet, a large amount of information is stored on web pages. In order to easily obtain this information, crawler technology came into being. A crawler is a program that automatically extracts web content and can help us collect large amounts of web data. However, in order to protect their data from being obtained by crawlers, many websites have adopted various anti-crawler methods. This article will introduce some anti-crawler processing methods and strategies for PHP crawlers to help developers deal with these limitations.

1. User-Agent camouflage

In HTTP requests, User-Agent is an identifier used to identify client applications, operating systems, hardware devices and other information. One of the common methods of anti-crawling is to identify and limit based on User-Agent. We can set the User-Agent to make the requests sent by the crawler look like requests from the browser.

Sample code:

<?php
// 设置User-Agent
$options = [
    'http' => [
        'header' => 'User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3',
    ],
];
$context = stream_context_create($options);

// 发送请求
$response = file_get_contents('http://example.com', false, $context);

// 处理响应
// ...
?>

2. IP proxy pool

Another common anti-crawler method is to restrict based on IP address. In order to circumvent this limitation, you can use an IP proxy, which forwards requests through an intermediate server to hide the real crawler IP address.

Sample code:

<?php
// 获取代理IP
$proxy = file_get_contents('http://api.example.com/proxy');

// 设置代理
$options = [
    'http' => [
        'proxy' => 'http://' . $proxy,
        'request_fulluri' => true,
    ],
];
$context = stream_context_create($options);

// 发送请求
$response = file_get_contents('http://example.com', false, $context);

// 处理响应
// ...
?>

3. Verification code identification

In order to prevent automatic access by crawlers, some websites will set verification codes to identify whether they are accessed by humans. In this case, we can use verification code recognition technology to crack the verification code in an automated way.

Sample code:

<?php
// 获取验证码图片
$imageUrl = 'http://example.com/captcha.jpg';
$ch = curl_init($imageUrl);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$image = curl_exec($ch);
curl_close($ch);

// 保存验证码图片
file_put_contents('captcha.jpg', $image);

// 识别验证码
$captchaText = recognize_captcha('captcha.jpg');

// 发送请求
$options = [
    'http' => [
        'header' => 'Cookie: captcha=' . $captchaText,
    ],
];
$context = stream_context_create($options);
$response = file_get_contents('http://example.com', false, $context);

// 处理响应
// ...
?>

<?php
// 验证码识别函数
function recognize_captcha($imagePath)
{
    // 调用验证码识别API，返回识别结果
    // ...
}
?>

Summary:

The above introduces some anti-crawler processing methods and strategies for PHP crawlers. When we face anti-crawler restrictions, we can circumvent these restrictions by disguising User-Agent, using IP proxy pools, and identifying verification codes. However, it should be noted that when crawling web page data, you must abide by the rules and laws and regulations of the website to ensure the legality of using crawler technology.

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