How to use PHP and Selenium to complete the development and practice of automated web crawlers

Crawler technology plays an important role in today’s digital era. Therefore, the development and practice of automated web crawlers came into being. Among web crawlers, PHP is a popular programming language, and Selenium is a powerful automated testing tool that can be used for automated browser control and web page data extraction. Next, we will introduce how to use PHP and Selenium to complete the development and practice of automated web crawlers.

1. Selenium installation and configuration

Before starting to use Selenium, we need to connect the Selenium server to our local computer. In addition, we also need a WebDriver so that Selenium can control the browser to operate. For Chrome browser, we need to download ChromeDriver and set it to the system path. The specific steps are as follows:

1.1 Download Selenium server

We can download Selenium server from the official website (http://www.seleniumhq.org/download/) to install Selenium.

1.2 Download ChromeDriver

Similarly, we can download ChromeDriver on the official website of ChromeDriver (http://chromedriver.chromium.org/downloads).

1.3 Set the system path

Add the downloaded ChromeDriver location to the system PATH variable to call ChromeDriver on the command line.

2. Installation and configuration of PHP

2.1 Download and install PHP

We can download and install PHP from the official PHP website (http://php.net/downloads .php) Download PHP and install it.

2.2 Install necessary PHP extensions

We need to install some PHP extensions so that PHP can communicate with the Selenium library. These extensions include php-curl and php-zip. Just enter the following command in the terminal:

sudo apt-get install php-curl
sudo apt-get install php-zip

3. combination of PHP and Selenium

After completing the installation and configuration of Selenium and PHP, we can start using them to Develop automated web crawlers.

3.1 Create a PHP script

We can write a PHP script from scratch, or find available scripts from the Internet. Below is an example of a PHP script using Selenium to access Google search and extract the results:

require_once('vendor/autoload.php');
use FacebookWebDriverRemoteRemoteWebDriver;
use FacebookWebDriverWebDriverBy;
 
// 设置WebDriver
$host = 'http://localhost:4444/wd/hub';
$capabilities = array(WebDriverCapabilityType::BROWSER_NAME => 'chrome');
$driver = RemoteWebDriver::create($host, $capabilities);
 
// 访问Google主页
$driver->get('https://www.google.com/');
 
// 通过ID查找搜索框并键入查询关键字
$searchBox = $driver->findElement(WebDriverBy::id('lst-ib'));
$searchBox->sendKeys('PHP and Selenium automated web scraper');
$searchBox->submit();
 
// 通过CSS选择器查找查询结果，并将结果存储到数组中
$results = $driver->findElements(WebDriverBy::cssSelector('div.g'));
foreach ($results as $result) {
    echo $result->getText() . "
";
}
 
// 关闭WebDriver
$driver->quit();

In this example, we have used findElement and findElements methods to find web page elements (i.e. Google search box and search results list). We also used the sendKeys method to type text into the search box and the submit method to submit the search form.

4. Some tips in practice

When developing automated web crawlers, there are some techniques that can improve our efficiency.

4.1 Use the correct classes

When using Selenium, we need to use the correct classes provided by the library to operate. For example, when looking for an element based on its ID attribute, we should use WebDriverBy::id to create a By class.

4.2 Avoid hard coding

Hard coding refers to including fixed values ​​or attributes directly in the code. Not only is this difficult to maintain, it also hinders the script's flexibility. Therefore, we should extract as many configurable variables and information into the script configuration file as possible.

4.3 Exception Handling

Because the content of web pages on the web is very changeable, various unexpected exceptions may occur when we extract data from web pages. To reduce the occurrence of this situation, we should implement exception handling in the code, such as try-catch blocks.

5. Summary

In this article, we introduced how to use PHP and Selenium to develop automated web crawlers and gave a sample script. We've also included some tips to help you make better use of this combination in practice. Automated web crawling is a very useful technology that can help us improve efficiency and obtain more data and information. Therefore, if you are doing web crawler development, PHP and Selenium will be your indispensable tools.

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