What engine is php based on?

Zend Engine

The Zend engine is the core of PHP implementation and provides the infrastructure for language implementation. As the core of the PHP language, Zend Engine exists in the Zend subdirectory of the PHP source code directory.

Why Zend Engine ?

  ·PHP3 adopts an operation mode of interpreting and executing at the same time, and the operating efficiency is very poor.

·The overall coupling of the code is relatively high, and the scalability is not good enough.

In 1997, Zeev Suraski and Andi Gutmans decided to rewrite the code to solve these two problems.

In the end, they named the core engine of this technology Zend Engine, and Zend means Zeev Andi.

Related recommendations: "php Basic Tutorial"

Zend Engine Function

First precompile (Compile), and then Execute again.

· Lexical analysis (Lexer): Divide the code into tokens Toekn.

·Grammar analysis (Parser): Grammar check.

·Generate operation code (opcode): Zend engine compiles these Tokens, compiles the code into opcode, and binds corresponding parameters and function calls.

·Execute: Zend engine executes these opcodes.

·Memory Management

The detailed process is as shown below:

PHP source code directory structure

/    ：主要包含一些说明文件以及设计方案。
Zend ：Zend 引擎的实现目录。包括词法语法解析，OPCODE，提供语言运行环境。
TSRM ：线程安全资源管理器。
build：放置一些和源码编译相关的一些文件。
ext  ：官方扩展目录。包括array系列，pdo系列，spl系列等函数的实现。
main ：最为核心的文件，实现PHP的基本设施。
pear ：PHP 扩展与应用仓库。
sapi ：各种服务器抽象层的代码。例如apache的mod_php，cgi，fastcgi以及fpm等等接口。
tests：PHP的测试脚本集合。
scripts：Linux 下的脚本目录。
win32：Windows平台相关的一些实现。

PHP Core

PHP Core consists of two parts: Zend Engine and PHP Core.

PHP Core is bound to the SAPI layer. PHP abstracts the communication with the upper "server" and abstracts and encapsulates all logic into SAPI.

For the upper-layer servers, their calls to PHP can be made through SAPI, achieving "decoupling and integration".

Common ways to call SAPI are:

·mod_php5: PHP module for Apache.

·CGI: Fork-And-Execute.

·Fastcgi: Long-Live type CGI.

·CLI: PHP command line mode.

The Architecture of PHP

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