How to use the PHP Curl class library to write an efficient crawler program?

How to use the PHP Curl class library to write an efficient crawler program?

Abstract: Crawler programs can be used to obtain data from web pages to achieve automated processing in various scenarios. This article will introduce how to use the PHP Curl class library to write efficient crawler programs and provide relevant code examples.

Introduction: With the increase in the popularity of the Internet, we deal with a large number of web pages every day. Sometimes, we need to obtain some useful data from the network, then we need to use a crawler program. A crawler program is a tool that automatically collects data. It simulates browser behavior to obtain web page content and extract useful information. In this article, we will use the PHP Curl class library to write an efficient crawler program.

1. First, we need to install and configure the PHP Curl class library. You can use the following command to install:

sudo apt-get install php-curl

After the installation is complete, enable the Curl extension in the PHP configuration file.

2. Next, we will introduce how to use the PHP Curl class library to write an efficient crawler program. Please follow the steps below:

1. Create a PHP file named crawler.php.

2. Introduce the Curl class library into the file:

   require_once('simple_html_dom.php'); //Introduce the simple_html_dom class library
   $url = "https://www.example.com"; //URL to be crawled
   $html = file_get_html($url); //Get web page content
   ?>

3. Get web content. We can use Curl's get method to obtain web page content:

   $ch = curl_init(); //Initialize Curl
   curl_setopt($ch, CURLOPT_URL, $url); //Set the URL
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); //Save the result to a string without printing it out
   $html = curl_exec($ch); //Execute Curl request
   curl_close($ch); //Close the Curl connection
   ?>

4. Parse the web page content. We can use the simple_html_dom class library to parse HTML and obtain the data we need:

   $dom = new simple_html_dom(); //Create a simple_html_dom object
   $dom-> ;load($html); //Load HTML content
   //Use CSS selector to extract data
   $title = $dom->find('title', 0)->plaintext; // Get the title
   $content = $dom->find('.content', 0)->plaintext; //Get the content
   $links = $dom->find('a'); / /Get all links
   ?>

5. Store data. We can store the obtained data in the database, or save it as a file:

   //Save the data to the database
   $conn = mysqli_connect("localhost", " username", "password", "database"); //Connect to the database
   $query = "INSERT INTO table (title, content) VALUES ('$title', '$content')"; //Construct an insert statement
   mysqli_query($conn, $query); //Perform the insertion operation
   mysqli_close($conn); //Close the database connection

   //Save the data as a file
   $file = fopen ("data.txt", "w"); //Open the file for writing
   fwrite($file, "Title: $title
   "); //Write the title
   fwrite( $file, "Content: $content
   "); //Write content
   fclose($file); //Close file
   ?>

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