Essential skills for automated crawlers: introduction to the use of PHP and Selenium

In today's digital era, crawling data on the Internet has become a common demand. For large-scale data collection and analysis, the use of automated crawlers is very necessary. Selenium is a widely used tool for web testing and automation, while PHP is a popular web programming language. In this article, we will introduce how to use PHP and Selenium to implement automated crawlers and crawl the required data.

1. Install Selenium and WebDriver

Before using Selenium, you need to download Selenium. It can be installed by:

composer require php-webdriver/webdriver

This way you can successfully download the webdriver and use it in your code. Next, we need to install the browser's webdriver, such as Chrome webdriver so that the program can call it. You can download the corresponding version of webdriver from the Chrome official website.

2. Basic usage of Selenium

After installing Selenium and webdriver, we can use it to automatically operate the browser. The following is a simple code example:

use FacebookWebDriverRemoteRemoteWebDriver;
use FacebookWebDriverWebDriverBy;

$driver = RemoteWebDriver::create('http://localhost:9515', DesiredCapabilities::chrome());
$driver->get('http://www.google.com');
$element = $driver->findElement(WebDriverBy::name('q'));
$element->sendKeys('Selenium');
$element->submit();
echo $driver->getTitle();

This code snippet first creates a remote webdriver object and connects to the local Chrome browser. It then opens Google, enters "Selenium" and performs a search. Finally, the page title of the browser is output.

3. Using Selenium for crawling

With the basic knowledge of Selenium, we can start using it to build an automated crawler. The following is a simple code example that can crawl all links in a specified web page:

use FacebookWebDriverRemoteRemoteWebDriver;
use FacebookWebDriverWebDriverBy;

$driver = RemoteWebDriver::create('http://localhost:9515', DesiredCapabilities::chrome());
$driver->get('https://www.example.com');

$links = $driver->findElements(WebDriverBy::tagName('a'));

foreach ($links as $link) {
    $url = $link->getAttribute('href');
    echo $url . "

";

}

This code snippet uses Selenium to access a website and obtain the website All links in the link. Get the value of the href attribute by traversing each link and calling the getAttribute('href') function, and finally output all the found links.

4. Implement automated crawler with PHP

The above code example uses Selenium code implemented in PHP. By combining Selenium and PHP, we can implement a complete automated crawler. The following is a sample code that uses paging technology to crawl Baidu search results The first 10 pages:

use FacebookWebDriverRemoteRemoteWebDriver;
use FacebookWebDriverWebDriverBy;

$driver = RemoteWebDriver::create('http://localhost:9515', DesiredCapabilities::chrome());
$driver->get('https://www.baidu.com/s?wd=php');

$pageNumber = 10;

for ($i = 1; $i <= $pageNumber; $i++) {
     echo "page {$i}

";

     $links = $driver->findElements(WebDriverBy::xpath('//div[@class="result c-container "]//h3[@class="t"]/a'));

     foreach ($links as $link) {
         $url = $link->getAttribute('href');
         echo $url . "

";

     }

     $nextPageElement = $driver->findElement(WebDriverBy::xpath('//a[@class="n" and contains(text(),"下一页>")]'));

     $driver->executeScript("arguments[0].scrollIntoView();", [$nextPageElement]);

     $nextPageElement->click();
 }

The above code snippet first opens the Baidu search results page, and then traverses all searches on each page As a result, the link address of each search result is output. After traversing a page, it will scroll to the bottom of the page and click the button of the next page to continue crawling more links.

Summary

Using Selenium and PHP to build automated crawlers is a very effective way. Selenium provides many of the core features needed to build automated crawlers, while PHP provides Selenium with a fast, easy and convenient way to achieve automation Crawlers. By mastering these skills, we can better utilize automated crawlers to collect the data we need quickly and efficiently.

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