PHP crawler practice: how to crawl web table data

With the advent of the Internet and big data era, more and more data can be collected and utilized. Among the many methods of obtaining data from web pages, crawler technology can be said to be the most powerful and efficient one.

In actual application scenarios, we often need to grab specific data from web pages, especially table data in web pages. Therefore, this article will introduce how to use PHP crawler technology to obtain and parse tabular data in web pages.

1. Install and configure the PHP crawler library

Before we start writing crawler code, we need to install and configure a PHP crawler library. Here we choose to use the PHP Simple HTML DOM Parser library, which is a lightweight HTML parser that can easily parse tags and attributes in HTML documents and provides some commonly used DOM operation methods. The library can be easily installed and configured using the composer tool.

2. Analyze the target web page

Before writing the code to capture web page data, we need to analyze the structure and data format of the target web page first so that we can correctly locate and obtain it. required data. Here we take the article list page of a blog website as an example. It contains multiple rows of data and some table elements, as shown below:

<table>
  <thead>
    <tr>
      <th>编号</th>
      <th>标题</th>
      <th>作者</th>
      <th>发布时间</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>1</td>
      <td><a href="/articles/1">PHP爬虫实战</a></td>
      <td>张三</td>
      <td>2022-06-01 08:00:00</td>
    </tr>
    <tr>
      <td>2</td>
      <td><a href="/articles/2">Python数据可视化</a></td>
      <td>李四</td>
      <td>2022-06-02 09:00:00</td>
    </tr>
    <!-- more rows -->
  </tbody>
</table>

The table in this web page is composed of <table># It consists of tags such as ##, <thead><code>, and , among which Used to define the column headers of the table, is used to define the row data of the table, is used to define the cell data, and tag represents the link to the article title.

Writing crawler code

With the analysis results of the target web page, we can write crawler code to obtain table data.

First, we need to load the target web page, and then use the

file_get_html() method to convert it into a DOM object. Then, we can use the find() method to select the element where the data is located. For example, table > tbody > tr means selecting the child of

All tags under element , that is, all rows of data in the table. The code is as follows:

$url = 'http://example.com/articles';
$html = file_get_html($url);

$rows = array();
foreach ($html->find('table > tbody > tr') as $row) {
  // 解析表格数据
}

Then, we need to traverse each row of data, parse the cell data and save it to an array for subsequent processing. Specifically, we can use the

find('td') method to select the child elements

of each row element, and then obtain its text content or link address. The code is as follows:

$url = 'http://example.com/articles';
$html = file_get_html($url);

$rows = array();
foreach ($html->find('table > tbody > tr') as $row) {
  $data = array();
  
  // 获取单元格文本内容或链接地址
  $columns = $row->find('td');
  $data['id'] = $columns[0]->plaintext;
  $data['title'] = $columns[1]->find('a', 0)->plaintext;
  $data['link'] = $columns[1]->find('a', 0)->href;
  $data['author'] = $columns[2]->plaintext;
  $data['date'] = $columns[3]->plaintext;
    
  $rows[] = $data;
}

In the above code, the

$data array saves the data of the current row, among which id, title, author and date correspond to the columns of the table respectively, while link is the link address of the article title. Use the $rows[] = $data statement to add the $data array to the $rows array.

Finally, we can further process and store the data according to needs, such as saving the data to a database or exporting it to an Excel file.

Summary

This article introduces how to use the PHP Simple HTML DOM Parser library to crawl web table data. By analyzing the structure and data format of the target web page and using the corresponding DOM operation methods, we can quickly locate and obtain the required data, thereby realizing various data analysis and application scenarios. Of course, crawler technology also needs to pay attention to comply with the website's usage regulations and policies, and cannot overuse or infringe on the rights of others.

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