A practical guide to automated web crawlers: building web crawlers with PHP and Selenium

Web crawlers have become one of the most important tools in today's Internet world. They can automatically browse various websites on the Internet and extract useful information that people need. The core technology of automated web crawlers is to use programming languages ​​​​and various tools to build a program that can automatically process data.

In recent years, Selenium has become one of the most popular tools in the field of automated web crawlers. It is a cross-browser automated testing tool that can simulate users performing various operations in the browser, such as clicking, scrolling, typing, etc., and can also obtain data from web pages. This makes Selenium ideal for building automated web crawlers, as it allows programs to obtain data in the same way as regular users.

This article will introduce how to use PHP and Selenium to build an automated web crawler. The crawler program introduced in this article will automatically browse the specified website and extract relevant information such as the title, author, publication date and article link of all articles, and finally save them to a CSV file.

Before we start, we need to install PHP, Selenium and WebDriver (corresponding to the browser driver). The following are the details of this article:

1. Environment settings and basic configuration

First, we need to install PHP in the local environment. PHP 7 or higher is recommended. Next, to install Selenium, you can do so using Composer. Use the composer command in the project folder to install it. After the installation is successful, we can start writing PHP programs.

2. Calling WebDriver and Selenium API

Before using Selenium to build an automated web crawler, we need to call WebDriver and create a WebDriver instance to communicate with the specified browser. WebDriver is a browser driver interface, and different browsers require different WebDrivers.

In PHP, we can use Selenium's PHP client library to create a WebDriver instance and bind it to the WebDriver of the specified browser. The following is a sample code:

require_once 'vendor/autoload.php';
use FacebookWebDriverRemoteDesiredCapabilities;
use FacebookWebDriverRemoteRemoteWebDriver;

// 配置浏览器类型、路径、驱动、和端口
$capabilities = DesiredCapabilities::chrome();
$driver = RemoteWebDriver::create('http://localhost:4444/wd/hub', $capabilities);

3. Establishing a browser session and opening the target website

Creating a browser session only requires one line of code, and we can choose our favorite browser ( Firefox or Chrome).

Here, we will use the Chrome browser. The following is the sample code:

// 使用Chrome浏览器打开目标网站
$driver->get('https://example.com');

4. Find and extract data

After opening the target website and loading the page, we need to locate and obtain the elements of the required data. In this example, we will find the title, author, publication date, and article link of all articles in the target website.

The following is sample code:

// 查找所有文章标题
$titles = $driver->findElements(FacebookWebDriverWebDriverBy::cssSelector('article h2 a'));

// 查找作者名字
$author_names = $driver->findElements(FacebookWebDriverWebDriverBy::cssSelector('article .author-name'));

// 查找发布日期
$release_dates = $driver->findElements(FacebookWebDriverWebDriverBy::cssSelector('article .release-date'));

// 查找文章链接
$links = $driver->findElements(FacebookWebDriverWebDriverBy::cssSelector('article h2 a'));

The following is sample code to find and extract data for each article:

$articles = array();

foreach ($titles as $key => $title) {
    // 提取标题
    $article_title = $title->getText();

    // 提取作者
    $article_author = $author_names[$key]->getText();

    // 提取发布日期
    $article_date = $release_dates[$key]->getText();

    // 提取文章链接
    $article_link = $links[$key]->getAttribute('href');

    // 添加文章到数组
    $articles[] = array(
        'title' => $article_title,
        'author' => $article_author,
        'date' => $article_date,
        'link' => $article_link
    );
}

5. The results are saved to a CSV file

The final step is to save the extracted data to a CSV file. Data can be stored into a CSV file using the PHP built-in function fputcsv().

The following is the sample code:

// 文件流方式打开文件
$file = fopen('articles.csv', 'w');

// 表头
$header = array('Title', 'Author', 'Date', 'Link');

// 写入标题
fputcsv($file, $header);

// 写入文章数据
foreach ($articles as $article) {
    fputcsv($file, $article);
}

// 关闭文件流
fclose($file);

This ends the content extraction and data processing. The data in the CSV file can be used for subsequent analysis and application. In addition, the data can be imported into other databases for further processing.

In summary, in this article, we have learned how to build an automated web crawler using PHP and Selenium, and how to obtain and process the data of the target website and save it to a CSV file. This example is just a simple demonstration, which can be applied to various scenarios where data needs to be obtained from the website, such as SEO, competitive product analysis, etc.

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