Explore the working principles, similarities and differences between PHP CLI and CGI

Working principles and similarities and differences

In Web development, PHP is a commonly used programming language, which can interact with the Web server in different ways, among which The most common ones are through PHP CLI (Command Line Interface) and PHP CGI (Common Gateway Interface). This article will explore the working principles, similarities and differences between PHP CLI and CGI, and provide specific code examples to illustrate the differences between them.

1. How PHP CLI works

PHP CLI is a PHP interpreter that runs under the command line. It executes PHP scripts by inputting parameters on the command line without relying on a web server. The working principle of PHP CLI can be simply divided into the following steps:

1. The user enters instructions on the command line to start PHP CLI.
2. The PHP CLI interpreter reads the commands entered by the user and loads the specified PHP script file.
3. PHP CLI executes the code in the PHP script file and displays the output results on the command line.

The following is a simple PHP CLI script example (test.php):

<?php
echo "Hello, PHP CLI!";

Users can run the script through the command line:

php test.php

The execution result will be Display "Hello, PHP CLI!" on the command line.

2. How PHP CGI works

PHP CGI is a way to interact with PHP scripts and web servers (such as Apache, Nginx, etc.). When the browser requests a PHP script, the web server calls the PHP interpreter to execute the PHP script and returns the execution results to the browser. The working principle of PHP CGI can be simply divided into the following steps:

1. The browser sends a request to the Web server to request a PHP script.
2. After the Web server receives the request, it calls the PHP CGI program to execute the PHP script.
3. PHP CGI executes the PHP script and returns the execution results to the web server.
4. The Web server returns the execution results to the browser for display.

The following is a simple PHP CGI script example (test.php):

<?php
echo "Hello, PHP CGI!";

Users can request the script through the browser, and the web server will call the PHP interpreter to execute the script , and returns the results to the browser for display.

3. Similarities and differences between PHP CLI and PHP CGI

1. The working methods are different: PHP CLI runs PHP scripts through the command line and does not rely on the web server; PHP CGI runs through The web server calls the PHP interpreter to execute PHP scripts and interact with the web server.
2. The operating environments are different: PHP CLI is suitable for PHP script execution in the command line environment; PHP CGI is suitable for PHP script execution in the web server environment.
3. The output methods are different: the output results of PHP CLI are displayed in the command line; the output results of PHP CGI are displayed in the browser.
4. The calling methods are different: PHP CLI is called and executed through the command line; PHP CGI is called and executed through the web server.

4. Code Example

The following is a comprehensive example, including a script (index.php) that can be run through PHP CLI and PHP CGI:

<?php
if (PHP_SAPI == 'cli') {
    // PHP CLI环境
    echo "Hello, PHP CLI!";
} else {
    // PHP CGI环境
    echo "Hello, PHP CGI!";
}

Users can run the script in the command line through the following command:

php index.php

Or request the script through a web browser, the web server will call the PHP interpreter to execute the script and return the results.

Through the above introduction, we can see the difference in the working principles and usage methods of PHP CLI and PHP CGI. Developers can choose the appropriate method to execute PHP scripts according to specific needs.

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