Introduction to the underlying development principles of PHP: from interpreter to underlying module

PHP is a scripting language widely used in website development. It is loved by developers because of its simplicity, ease of learning and rapid development. However, as a low-level developer, the depth of understanding of PHP's underlying development principles directly affects the ability to code optimization, performance tuning, and function expansion. This article introduces the underlying development principles of PHP from the interpreter to the underlying modules, helping readers gain a deeper understanding of PHP's underlying implementation principles.

1. PHP interpreter
PHP interpreter is a key part that parses and compiles PHP code into an executable instruction set and executes it line by line. Currently, PHP has two mainstream interpreter versions: Zend Engine and HHVM. Zend Engine is the most commonly used interpreter and is popular due to its compact design and excellent performance; HHVM is an interpreter developed by Facebook and has just-in-time compilation (JIT) features and even better performance.

The main work of the interpreter includes lexical analysis, syntax analysis, semantic analysis and instruction generation. Lexical analysis converts the source code into a series of "lexical tokens", such as identifiers, constants, operators, etc.; syntactic analysis organizes the lexical tokens to form a grammatical structure and generates a syntax tree; semantic analysis performs type checking and Semantic verification ensures the correctness of the program; instruction generation converts the syntax tree into an executable instruction set.

2. PHP’s kernel module
PHP’s kernel module consists of a series of underlying C functions, providing the ability to interact with the operating system, file system, database, etc. These low-level functions include file reading and writing, directory operations, logging, network communication, encryption and decryption, memory management, etc. These low-level functions are the basis of the PHP language, through which we can develop powerful applications.

The development of underlying modules requires familiarity with the kernel programming interface (API) of C language and PHP, as well as knowledge of cross-platform development. By writing low-level modules, we can improve the performance of PHP, expand the functionality of PHP, and even develop some advanced features and functions.

3. PHP extension modules
In addition to the kernel module, PHP also supports extending its functions through extension modules. The extension module can be a dynamic link library written in C or a script file written in PHP. PHP provides a wealth of extension interfaces for developers to develop their own extension modules.

PHP extension modules can be used to enhance PHP functions, such as database extensions, image processing extensions, cache extensions, etc.; they can also be used to optimize performance, such as accelerator extensions, cache extensions, etc. By developing our own extension modules, we can customize the functions and performance of PHP according to actual needs to achieve the effects we want.

4. PHP’s underlying optimization skills
In the underlying development of PHP, optimization is a very important link. Through some low-level optimization techniques, the performance of PHP can be significantly improved.

The first is the optimization of the PHP interpreter. You can improve PHP performance by adjusting PHP execution parameters, such as adjusting memory limits, adjusting compilation options, turning on caching, etc. You can also optimize PHP code in a targeted manner, such as avoiding the use of eval functions, avoiding the use of global variables, etc.

The second is the optimization of the underlying modules. The performance of PHP can be improved by improving the efficiency of the underlying modules, such as optimizing file read and write operations, optimizing network communication, etc.; concurrency performance can also be improved through technologies such as multi-threading and asynchronous operations.

Finally, use appropriate extension modules to optimize PHP. Choosing appropriate extension modules can improve the functionality and performance of PHP, such as using PHP's own cache extension, using third-party accelerator extensions, etc.

Summary:
This article briefly introduces the underlying development principles of PHP from the interpreter to the underlying module. Understanding the underlying development principles of PHP plays an important role in program tuning, performance optimization, and function expansion. Through in-depth study and practice, we can better understand the underlying implementation principles of PHP, thereby improving our development capabilities.

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