How does PHP work?

PHP is an interpreted scripting language. Its operation can be described as follows:

1. Client request: The client's web browser sends an HTTP request to the web server (e.g., Apache, Nginx).
2. Request forwarding: The web server recognizes the requested file has a .php extension and passes control to the PHP interpreter.
3. Parsing and compilation: The PHP interpreter (Zend Engine) reads the PHP code, performs syntax analysis, and compiles it into intermediate bytecode.
4. Bytecode execution: Zend Engine executes the generated bytecode. During execution, PHP can interact with databases, file systems, and other services.
5. Response formation: The result of execution is the generated HTML, CSS, JavaScript, or other content.
6. Response transmission: The generated output is sent back to the web server.
7. Client delivery: The web server sends this output as an HTTP response to the client's web browser, which displays it.

Example of a simple PHP script:

<?php
// Simple PHP script
$name = "World";
echo "Hello, " . $name . "!"; // Outputs "Hello, World!" in HTML
?>

Key components:

• PHP interpreter (Zend Engine): The core that executes code.
• SAPI (Server API): Facilitates interaction between PHP and the web server (e.g., mod_php for Apache, php-fpm for Nginx).
• Extensions: Add functionality (database access, image processing, etc.).