An introductory guide to the underlying development principles of PHP7: Learn the secrets of the PHP kernel from scratch

Introduction Guide to PHP7 Underlying Development Principles: Learn the Mysteries of PHP Kernel from Scratch

Introduction:

With the rapid development of the Internet, PHP as A popular server-side scripting language with a wide range of application scenarios. However, many people know very little about the internals and workings of PHP. For developers who want to understand the PHP kernel in depth, this article will provide an introductory guide to help them learn the mysteries of the PHP kernel from scratch.

1. Basic concepts of PHP kernel

1. Compilation process of PHP

In the compilation process of PHP, the source code will first go through the lexical analyzer Convert it into a series of tokens (Tokens), then convert these tokens into an abstract syntax tree (AST) through a syntax analyzer, and finally generate executable machine code through an interpreter or compiler.

2. PHP execution process

PHP execution process can be divided into two stages: interpretation execution and compilation execution. During the interpretation and execution phase, PHP will parse the source code line by line and perform corresponding operations. During the compilation and execution phase, PHP will compile the source code into intermediate code (Opcode) form, and store these intermediate codes in memory to improve execution efficiency.

2. The structure of the PHP kernel

1. Zend engine

The Zend engine is the core component of the PHP kernel. It is responsible for converting source code into intermediate code. , and is responsible for the execution of intermediate code.

2. Memory Management

The PHP kernel contains a complete set of memory management mechanisms for managing the allocation and release of data structures such as variables, functions, and classes.

3. Extensions

The PHP core provides an extensibility mechanism that allows developers to create custom extension modules to enhance the functionality of PHP. Extensions can be loaded and unloaded dynamically and can call PHP intrinsic functions.

3. Examples of PHP kernel: memory management

The following takes PHP memory management as an example to introduce how to learn the mysteries of PHP kernel from scratch.

1. Creation and destruction of variables

The PHP kernel allocates memory space for each variable and releases it when the variable is no longer used. The following is a sample code:

<?php
$a = "Hello";  //创建一个字符串变量
unset($a);    //销毁变量
?>

2. Reference counting

The PHP kernel uses a reference counting mechanism to track the number of references to variables. When a variable is referenced, the reference count increases by one; when a variable is no longer referenced, the reference count decreases by one. Only when the reference count reaches zero, the PHP kernel will release the memory space it occupies. The following is a sample code:

<?php
$a = "Hello";  //创建一个字符串变量
$b = $a;      //变量之间的赋值是引用传递
unset($a);    //销毁变量
?>

3. Garbage Collection

In addition to reference counting, the PHP kernel also implements a garbage collection mechanism to release useless memory space. The garbage collector periodically scans the memory space to determine which variables are no longer in use and releases the memory space they occupy.

IV. Conclusion

This article briefly introduces the underlying development principles of PHP7, and focuses on the basic concepts, structure and memory management examples of the PHP kernel. I hope this article can help developers who want to learn more about the PHP core get started and inspire them to explore more mysteries.

Reference materials:

1. PHP Internals Book（https://phpinternals.net/）
2. Zend Engine Documentation（https://www.php.net /manual/en/internals2.php)

Code sample reference:

1. PHP source code (https://github.com/php/php-src)
2. PHP extension example (https://github.com/php/pecl-php-xxx)

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