How to use PHP web crawler to crawl Zhihu

With the rapid development of the Internet, the era of information explosion has arrived. As a high-quality question and answer platform, Zhihu has rich knowledge and a large amount of user information. For crawler developers, Zhihu is undoubtedly a rare treasure.

This article will introduce a method of using PHP language to write a web crawler to crawl Zhihu data.

1. Determine the target data

Before starting to write a web crawler, we need to first determine the data that needs to be crawled. For example, we may want to obtain questions and their answers, user information, etc. on Zhihu.

2. Analyze the page structure

By using the browser's developer tools, we can easily analyze the structure of the Zhihu page. Before analysis, we can first open the Zhihu homepage, then press the F12 key and select the "Elements" tab. This step will allow us to see the HTML code for the page.

By observing the HTML code, we can find the element where the data that needs to be crawled is located and the corresponding class name or ID name. For example, if we want to get the title of a question, we can find the HTML tag of the question and see its corresponding class name or ID name. This information will play an important role when writing crawler code later.

3. Send HTTP requests and parse response data

When using PHP to write a crawler program, we can use the cURL library to send HTTP requests and obtain response data. The following is a simple example:

$url = 'https://www.zhihu.com/question/123456789';
$curl = curl_init($url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($curl);
curl_close($curl);

In the above example, we use the cURL library to send an HTTP request to a question on Zhihu and save the response data. Next, we can use PHP libraries such as DOMDocument or SimpleXMLElement to parse the response data.

4. Extract the required data

After parsing the response data, we need to analyze the HTML document and extract the required data. This can be achieved by using PHP libraries such as DOMXPath or regular expressions.

For example, if we want to get all the answers to a question on Zhihu, we can first use DOMXPath to get the HTML elements where all the answers are located, and then extract the required data from these elements.

$doc = new DOMDocument();
$doc->loadHTML($response);
$xpath = new DOMXPath($doc);
$answer_elements = $xpath->query("//div[@class='List-item']");

foreach ($answer_elements as $element) {
    // 使用DOMElement的方法获取答案的标题、作者、发布时间等信息
}

5. Storing data

Finally, we can store the extracted data into a database or file. If we want to save data to the database, we can use PHP MySQLi or PDO library to achieve this. If we want to save data to a file, we can use PHP file manipulation libraries such as fopen and fwrite to achieve this.

$fp = fopen("data.csv", "w");
foreach ($data as $row) {
    fputcsv($fp, $row);
}
fclose($fp);

In the above example, we used the fputcsv function to save the data to the specified CSV file.

Summary

By using PHP to write a crawler program, we can easily crawl data on Zhihu. During the development process, we need to determine the target data, analyze the page structure, send HTTP requests and parse the response data, extract the required data, and store the data. The method introduced here is only a basic framework, and may need to be adjusted and optimized according to specific needs in actual development.

The above is the detailed content of How to use PHP web crawler to crawl Zhihu. For more information, please follow other related articles on the PHP Chinese website!