Making crawling easier: Developing web crawlers with PHP and Selenium

Let’s briefly introduce what a web crawler is. A web crawler is a program that automatically obtains web page information according to certain rules and is used to collect data on the Internet. In the Internet era, data acquisition is becoming more and more important, and so are web crawlers. This article uses PHP and Selenium to implement a simple web crawler.

1. The basic principle of a crawler

The basic principle of a crawler is to write a program to simulate browser behavior, send a request to the server, parse the returned content and extract useful data. We can analyze the HTML source code of the web page to get the tags or elements where the content we want to obtain is located, and then write a program to capture the content of these tags and elements.

2. Reasons for choosing PHP as the development language

PHP is a popular open source server scripting language. Because its code is simple, easy to learn, and easy to use, it is used by many websites. An important feature of PHP is its ability to run on many different system platforms. Additionally, PHP is an object-oriented language, making it easier to maintain and able to interact with many other languages.

3. Choose Selenium as an automated testing tool

Selenium is a popular web application testing tool. It can simulate human behavior in the browser and perform various testing tasks, including automated testing of websites and applications. Additionally, Selenium supports multiple programming languages, including PHP.

4. Installation and configuration environment

Using Selenium requires installing a browser driver, and the Chrome browser is used here.

1. Install the Chrome browser

When installing the Chrome browser, you need to ensure that the Chrome driver corresponds to the browser version.

2. Download the Chrome driver

You need to use the Chrome driver to control the behavior of the browser in the program. To download the driver, you can directly download the corresponding version from the official website and then unzip it.

3. Configure environment variables

Put the Chrome driver into the environment variable so that the program can find the driver file.

4. Install Selenium

Use Composer to install

composer require facebook/webdriver

5. Write code

The following is a simple sample code for crawling Baidu Search box text on the homepage:

<?php
require_once __DIR__ . '/vendor/autoload.php';
use FacebookWebDriverRemoteDesiredCapabilities;
use FacebookWebDriverRemoteRemoteWebDriver;

//指定驱动路径
$chromeOptions = new FacebookWebDriverChromeChromeOptions();
$chromeOptions->addArguments(['--headless']);
$chromeOptions->setBinary('/Applications/Google Chrome.app/Contents/MacOS/Google Chrome');
$capabilities = DesiredCapabilities::chrome();
$capabilities->setCapability(FacebookWebDriverChromeChromeOptions::CAPABILITY, $chromeOptions);

//连接Chrome并打开百度首页
$driver = RemoteWebDriver::create('http://localhost:9515', $capabilities);
$driver->get('http://www.baidu.com/');

//模拟搜索
$element = $driver->findElement(FacebookWebDriverWebDriverBy::id('kw'));
$element->sendKeys('hello world');
$element->submit();

//获取搜索结果中的相关内容
$results = $driver->findElements(FacebookWebDriverWebDriverBy::className('result-title'));
foreach ($results as $result) {
    echo $result->getText() . "
";
}

//关闭浏览器
$driver->quit();

The above code uses Selenium to connect to Chrome and open the Baidu homepage, enter hello world in the search box, and then simulate submitting a search. Finally, capture the content in the search results and output it.

6. Implementation results

Using the above code can capture the keywords in the search box on Baidu's homepage. We can modify the code to crawl more websites and capture more data.

Selenium provides many perfect tools to automate web interface testing, but can also be used for web crawling. Using PHP to write crawler code and Selenium to simulate browser behavior, the crawler can easily access and extract large amounts of data.

7. Summary

This article introduces the use of PHP and Selenium to implement a simple crawler, including environment configuration and code implementation. This is a good starting point that can be expanded to larger projects and use more features. If you want to learn more about web crawlers, you can read crawler-related books and learn from other crawler code examples.

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