How PHP Works Internally

PHP (which stands for “PHP: Hypertext Preprocessor”) is a server-side scripting language designed primarily for web development. It’s a powerful tool that allows developers to create dynamic web pages.

Here’s a simplified overview of how PHP works:

• Client Request: A user navigates to a website by typing the URL into their browser. The browser sends a request to the server hosting the website.
• Server-side Processing: If the page they requested is a PHP page, the server recognizes the .php file extension and knows that it needs to interpret and execute the PHP code.
• PHP Interpreter: The PHP code is processed by a PHP interpreter that runs on the server. This is a program that reads the PHP code, interprets it, and executes the instructions.
• Data Interaction: During this process, the PHP code may interact with databases, other files, or other systems. For example, it might retrieve data from a database, process it, and use it to generate HTML code.
• Response: The server then sends a response back to the client’s browser. This response is typically a fully constructed HTML page. Importantly, only the resulting HTML (and JavaScript, CSS, etc.) is sent to the client, not the PHP code itself.
• Browser Displays the Page: The browser receives the response and displays the web page to the user. Any subsequent interactions may cause the browser to request more PHP pages, starting the cycle over again.

Internally, the PHP interpreter follows these steps:

• Lexing: The PHP code is read and converted into tokens. Tokens are like the basic building blocks of the language (like words in a sentence).
• Parsing: The tokens are processed by the parser, which checks that the code follows the grammar of the PHP language (similar to checking that a sentence follows the rules of grammar).
• Compilation: The parser produces an abstract syntax tree (AST), a tree-like representation of the code. This is then compiled into bytecode (a low-level representation of the code that is closer to machine language).
• Execution: Finally, the bytecode is executed. During execution, the PHP code might, for example, interact with a database or generate HTML.

Remember, this is a simplified explanation and the real process is more complex, with more steps and components involved. But hopefully, this provides a good layman’s overview of how PHP works internally.