Crawler development technology: Use PHP and Selenium to build a first-class web crawler

With the development of the Internet, crawler technology has become an indispensable tool in data acquisition, market analysis, competitive product research and other fields. Among traditional crawler technologies, Python is the preferred language for developing crawler tools. Compared with other languages, Python has the advantages of being easy to learn, concise, and rich in crawler libraries. But today, we are going to introduce another excellent crawler language-PHP, and its efficient techniques for combining with Selenium.

1. What is Selenium
Selenium is a tool that is widely used in web automation testing. Through Selenium, you can simulate human behavior to operate the website, and implement automated website testing and even crawler development. The core of Selenium is WebDriver, which can simulate browser behavior, including clicking, input, switching windows, and all other behaviors that require human operation. Selenium is very useful for crawlers that require login, verification and other complex scenarios.

2. Advantages of using Selenium to develop crawlers
1. Suitable for data crawling in complex scenarios
2. Can directly simulate human behavior and avoid problems with IP or Cookies
3. Including Java , Python, Ruby and other languages ​​supported

3. Selenium installation
Selenium can be installed directly in PHP. The installation method is as follows:

1. Install composer:
curl -sS https://getcomposer.org/installer | php

2. Create composer.json configuration file and add Selenium WebDriver package:

{
"require": {

"php-webdriver/webdriver": "dev-master"

}
}

3. Install WebDriver through composer:

php composer.phar install

4. Download WebDriver and unzip it:

wget https://selenium-release.storage.googleapis.com/2.53/selenium-server-standalone-2.53.1.jar

4. PHP Selenium crawler code practice
Let’s follow Selenium will be called to simulate Baidu search, search for relevant keywords and return crawling results.

First, you need to import WebDriver and start the browser:

require_once('vendor/autoload.php');
use FacebookWebDriverRemoteRemoteWebDriver;
use FacebookWebDriverWebDriverBy;

$host = 'http://localhost:4444/wd/hub';
$driver = RemoteWebDriver::create($host, array('browserName' => 'firefox'));

Next we enter the URL and find the search box:

$driver->get("http://www.baidu.com");
$element = $driver->findElement (WebDriverBy::id('kw'));

Enter keywords in the search box and perform a search:

$element->sendKeys("Selenium");
$element->submit();

Waiting for the browser to load completely, we find the position of the search results by looking for the next page button:

$driver->wait() ->until(
WebDriverExpectedCondition::elementToBeClickable(WebDriverBy::xpath("//a[contains(@class,'n') and contains(@class,'next')]"))
) ;

After finding the search results, we store the results into the $result array:

$result = array();
$elements = $driver->findElements(WebDriverBy: :cssSelector('h3 > a'));
foreach ($elements as $element) {
$result[] = array($element->getText(), $element->getAttribute( 'href'));
}

Finally, we close the browser and return the result:

$driver->quit();
echo json_encode($result) ;

The above is a practical code for a crawler based on PHP Selenium.

5. Summary
Selenium is an indispensable tool in web automated testing and crawler development. This article introduces the advantages of Selenium technology and how to use PHP to write Selenium crawlers. Although Python is still a more popular choice in crawler development, PHP, as an excellent language, combined with Selenium, can become a powerful crawler tool, providing more possibilities for data analysis, market research and other fields.

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