How to use PHP to implement a crawler program with anti-crawler function

With the development of Internet technology, the application of crawler programs is becoming more and more widespread. We can automatically obtain data on the Internet through crawler programs for data analysis and mining. As the number of crawlers increases, some websites have begun to use anti-crawler technology to protect their data. Therefore, in the process of using PHP to implement crawler programs, we also need to consider how to deal with the challenges of anti-crawler technology.

This article will introduce how to use PHP to implement a crawler program with anti-crawler function.

1. Determine the website to crawl

First, we need to determine the website we want to crawl. For some smaller websites, we can directly crawl their web pages and extract data. But for some large websites, they often use anti-crawler technology to prevent our crawling.

Therefore, when determining the website to be crawled, we need to first understand whether the website uses anti-crawling technology. If used, we need to understand the types and specific implementation methods of anti-crawler technology so that we can take corresponding countermeasures.

2. Use proxy IP

Proxy IP, which is the IP address of the proxy server. Using proxy IP can effectively hide our real IP address and prevent websites from learning about our crawler program. When using PHP to implement a crawler program, we can use the curl library to request web pages and inject the proxy IP when requesting.

Code example:

$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, 'http://www.example.com/');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_PROXY, 'proxy_ip:proxy_port');
$result = curl_exec($curl);
curl_close($curl);

In the above code, we use the curl library to request the website 'http://www.example.com/' and inject the proxy when requesting IP. This way we can successfully request and get the data for the website.

3. Use random UA

UA, that is, User Agent. When a browser accesses a website, it will send its own UA to the website to inform the website of the browser and operating system version used. Some websites will determine the true identity of visitors based on UA ​​and take corresponding anti-crawler measures.

Therefore, when using PHP to implement a crawler program, we can use random UA to avoid being identified by the website. We can use PHP's rand() function to generate random numbers and inject the random numbers into the curl request as UA.

Code example:

$ua_list = array(
    'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:83.0) Gecko/20100101 Firefox/83.0',
    'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.66 Safari/537.36',
    'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Edge/83.0.478.45',
);
$rand = rand(0, count($ua_list) - 1);
$ua = $ua_list[$rand];

$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, 'http://www.example.com/');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_PROXY, 'proxy_ip:proxy_port');
curl_setopt($curl, CURLOPT_USERAGENT, $ua);
$result = curl_exec($curl);
curl_close($curl);

In the above code, we define a $ua_list array, which stores multiple UAs. We use the rand() function to randomly select a UA and add It is injected into the curl request. In this way, our UA will change randomly every time we request it, which greatly improves the concealment of our crawler program.

4. Use verification code identification

When some websites recognize the crawler program, a verification code page will pop up to verify the visitor's true identity. If our crawler cannot parse the verification code correctly, it will cause the crawler to be unable to continue running.

Therefore, when using PHP to implement a crawler program, we can use verification code recognition technology to solve this problem. Verification code recognition technology mainly involves fields such as image processing and machine learning. We can use PHP's image processing library GD to process the verification code image, and use OCR technology to identify the verification code.

Code example:

$img = imagecreatefrompng('captcha.png');
$width = imagesx($img);
$height = imagesy($img);

for ($y = 0; $y < $height; $y++) {
    for ($x = 0; $x < $width; $x++) {
        $rgb = imagecolorat($img, $x, $y);
        $r = ($rgb >> 16) & 0xFF;
        $g = ($rgb >> 8) & 0xFF;
        $b = $rgb & 0xFF;

        // 处理验证码图片像素
    }
}

// 使用OCR识别验证码

In the above code, we use the imagecreatefrompng() function to read the verification code image into the $img object. Then we iterate through each pixel of the captcha image and process the RGB value of each pixel. Finally, we can use OCR technology to identify the verification code.

Summary

This article introduces how to use PHP to implement a crawler program with anti-crawler function. During the implementation process, we need to use proxy IP, random UA and other technologies to avoid being identified by the website, and we also need to use verification code identification technology to solve the verification code problem. I hope this article can be of some help to the implementation of PHP crawler programs.

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