How does PHP execute scripts: A step-by-step explanation

PHP Script Execution Explained: A Comprehensive Guide

PHP, a popular web development language, requires a thorough understanding of its execution process for efficient coding. This guide explores the intricate stages of PHP script execution, addressing the misconceptions and providing a detailed insight into the mechanics behind it.

The Evolution of PHP Compilation

Until PHP 3, scripts were directly interpreted and executed. However, with the release of PHP 4, PHP evolved into a compiled language. This introduced the Zend engine, a fundamental component responsible for transforming PHP source code into Zend opcodes.

The Zend Engine and Opcode Generation

The Zend engine separates PHP processing into two primary phases. In the first phase, PHP source code is parsed and converted into binary opcodes. These opcodes, analogous to Java bytecodes, contain a series of instructions. The constructed opcodes are then stored in memory.

Opcode Execution: The Second Phase

The second phase of Zend engine processing involves the execution of the generated opcodes. This phase iterates through the opcodes, executing each instruction sequentially. The interpretation of these instructions effectively executes the PHP script.

The Role of Included Files in Parsing

Included files are not parsed line-by-line within a PHP script. Instead, each include statement is processed at the beginning of the PHP script, allowing the included file's contents to be seamlessly incorporated into the main script's execution.

The above is the detailed content of How does PHP execute scripts: A step-by-step explanation. For more information, please follow other related articles on the PHP Chinese website!