How to implement a custom crawler framework using PHP

With the continuous development of the Internet, the amount of information has exploded, and obtaining valuable information has become a need for many people. In such an environment, crawler technology has gradually emerged and become one of the important tools in the big data era. Crawler technology has a wide range of applications and can be used in many fields such as network public opinion monitoring, data analysis, and information mining. This article will introduce how to implement a custom crawler framework using PHP.

1. Principle of crawler framework

A crawler is a program that automatically obtains web page information. It crawls web page text and extracts valuable data for analysis and utilization. The crawler framework is the basis of the crawler program, which includes customized acquisition, parsing, storage and other methods.

The crawler program is implemented through the crawler framework. The basic process is as follows:

1. Get web page information: Send a request to the target website through the HTTP protocol to obtain web page text information.
2. Parse web page information: parse web page text and extract target data for processing.
3. Storage processing results: Store the processed data for subsequent data analysis and utilization.

2. PHP crawler framework implementation

1. Get web page information

In PHP, HTTP requests can be implemented through the CURL library. CURL is a powerful open source network library that can be used to process URLs (Uniform Resource Locator, Uniform Resource Locator) in PHP.

The code is as follows:

$ch = curl_init();  // 初始化 cURL
$options =  array(
    CURLOPT_URL => $url,  // 请求的 URL
    CURLOPT_RETURNTRANSFER => 1,  // 返回原生的输出内容
    CURLOPT_ENCODING => '',  // 自动处理响应头中的 Transfer-Encoding
    CURLOPT_USERAGENT => $_SERVER['HTTP_USER_AGENT']  // 模拟 user-agent
);
curl_setopt_array($ch, $options); 
$result = curl_exec($ch);  // 执行请求
curl_close($ch);  // 关闭请求链接

In the above code, first Use the curl_init() function to initialize CURL, and then use the curl_setopt_array() function to set various parameters of the CURL request, including the requested URL, returning native output content, automatically processing Transfer-Encoding in the response header, and simulating user-agent. Finally, execute the request through curl_exec() and close the request link. After executing the above code, you can successfully obtain the web page information of the target website.

2. Parsing web page information

In PHP, you can use the DOMDocument class to parse HTML text, which provides a set of DOM (Document Object Model, Document Object Model) interface, which can easily parse HTML text.

The code is as follows:

$doc = new DOMDocument();
$doc->loadHTML($result);  // 加载 HTML 内容
$xpath = new DOMXPath($doc);
$tags = $xpath->query('//tag')  // 获取指定标签
foreach ($tags as $tag) {
    // 对标签内容进行解析
}

The above code first creates an object of the DOMDocument class, then loads the web page text through the loadHTML() function, then obtains the specified tag through the DOMXPath class, and performs the tag content parse.

3. Storage processing results

In PHP, data can be stored through the MySQL database, which provides a set of PDO (PHP Data Objects, PHP Data Objects) interface , you can easily perform database operations.

The code is as follows:

$pdo = new PDO('mysql:host=$dbhost;dbname=$dbname', $username, $password); // 连接数据库
$sql = 'INSERT INTO table_name (field1, field2, ...) VALUES (:value1, :value2, ...)';  // SQL 语句
$stmt = $pdo->prepare($sql);  // 预处理 SQL 语句
$stmt->bindParam(':param1', $value1);  // 绑定参数
$stmt->bindParam(':param2', $value2);
...
$stmt->execute();  // 执行 SQL 语句

In the above code, first use the PDO object to connect to the MySQL database, then use SQL statements to insert data into the specified data table, and bind parameters by preprocessing the SQL statements. Afterwards, the data can be successfully stored in the database by directly executing the SQL statement.

3. Crawler framework use case

After implementing the crawler framework, we can use it to crawl any website. A simple use case will be demonstrated below. For example, we now need to crawl Zhihu user information. First, we need to obtain the user's page information:

$url = "https://www.zhihu.com/people/xxx";
$result = getCurl($url);

Then, we parse the returned page information through XPath and obtain the target information:

$doc = new DOMDocument();
$doc->loadHTML($result);
$xpath = new DOMXPath($doc);
// 用户名
$username = $xpath->query("//*[@class='ProfileHeader-name']/text()")->item(0)->nodeValue;
// 签名
$userbio = $xpath->query("//div[@class='ProfileHeader-headline']/span//@title")->item(0)->nodeValue;
// 关注数
$following_count = $xpath->query("//*[@class='NumberBoard-itemValue']/text()")->item(2)->nodeValue;
// 粉丝数
$followers_count = $xpath->query("//*[@class='NumberBoard-itemValue']/text()")->item(3)->nodeValue;

Finally, we can use the MySQL database to store the obtained target information:

$pdo = new PDO('mysql:host=localhost;dbname=database', 'username', 'password');
$sql = "INSERT INTO `zhihu_users`(`username`, `userbio`, `following_count`, `followers_count`, `updated_at`) VALUES (:username, :userbio, :following_count, :followers_count, NOW())";
$stmt = $pdo->prepare($sql);
$stmt->bindParam(':username', $username);
$stmt->bindParam(':userbio', $userbio);
$stmt->bindParam(':following_count', $following_count);
$stmt->bindParam(':followers_count', $followers_count);
$stmt->execute();

Through the above code example, we can see the process of using PHP to implement a custom crawler framework, including obtaining web page information , parse web page information and store processing results and other operations. Through this framework, we can easily crawl and analyze the target website and improve the efficiency and accuracy of data application.

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