What language is the underlying language of php?

The bottom layer of php is C language, so if you want to study the underlying code, you need to master C language related knowledge.

PHP itself is implemented in C, so the functions that are ultimately called are all C functions. In fact, you can Think of PHP as a software developed in C. (Recommended learning: PHP video tutorial)

php’s zend engine, including lexical analysis, syntax analysis, AST, etc. requires knowledge of compilation principles.

Zend engine: Pure C implementation, which is the core part of PHP. It translates PHP code (lexical, syntax analysis and a series of compilation processes) into executable opcode processing and implements the corresponding The processing method implements basic data structures (such as hashtable, oo), memory allocation and management, and provides corresponding api methods for external calls. It is the core of everything, and all peripheral functions are implemented around Zend.

Extensions: Revolving around the Zend engine, extensions provide various basic services in a component-based manner. Our common various built-in functions (such as array series), standard libraries, etc. are all implemented through extensions.

Sapi:The full name is Server Application Programming Interface. Sapi uses a series of hook functions to enable PHP to interact with peripheral data. This is a very elegant and successful PHP Design, through sapi, successfully decouples and isolates PHP itself from upper-layer applications. PHP can no longer consider how to be compatible with different applications, and the application itself can also implement different processing methods according to its own characteristics.

Some common sapis are:

apache2handler: This is the processing method when using apache as the webserver and running in mod_PHP mode, and it is also now The most widely used one.

cgi: This is another direct interaction method between webserver and PHP, which is the famous fastcgi protocol. In recent years, fastcgi PHP has been used more and more, and it is also an asynchronous webserver. The only supported method.

cli:Upper-layer application of application mode called by command line: This is the PHP program we usually write. We can obtain various application modes through different sapi methods, such as through webserver. Web applications, running as scripts on the command line, etc.

Upper-layer application: This is the PHP program we usually write. We can obtain various application modes through different sapi methods, such as implementing web applications through webserver, and using Run in script mode, etc.

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