The basics of how PHP works

This article mainly introduces the basics of the working principle of PHP. It has a certain reference value. Now I share it with everyone. Friends in need can refer to it.

I recently built a server and suddenly felt like a lamp. How exactly does it work, or how is it connected? I usually just write programs, and I have never thought about the working principle between them:

The underlying working principle of PHP

Figure 1 PHP structure

As can be seen from the picture, PHP is a 4-layer system from bottom to top

①Zend engine

Zend as a whole is implemented in pure C and is the core part of PHP. It combines PHP code with Translation (a series of compilation processes such as lexical and syntax analysis) processes executable opcodes and implements corresponding processing methods, implements basic data structures (such as hashtable, oo), memory allocation and management, and provides corresponding API methods for External calls are the core of everything, and all peripheral functions are implemented around zend.

②Extensions

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 through extensions To achieve this, users can also implement their own extensions as needed to achieve function expansion, performance optimization and other purposes (for example, the PHP middle layer and rich text parsing currently used by Tieba are typical applications of extensions).

③Sapi

The full name of Sapi is Server Application Programming Interface, which is the server application programming interface. Sapi allows PHP to interact with peripheral data through a series of hook functions. This is PHP's very elegant and A successful design successfully decouples and isolates PHP itself from upper-layer applications through SAPI. 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. We will introduce it later in the sapi chapter

④Upper-layer application

This is the PHP program we usually write. We can obtain various application modes through different sapi methods, such as implementing web through webserver Apply, run as a script from the command line, etc.

Architectural ideas:

The engine (Zend) component (ext) model reduces internal coupling

The middle layer (sapi) isolates the web server and php

************************************************ ****************************

If php was a car, then

The framework of the car is php itself

Zend is the engine of the car

The various components below Ext are the wheels of the car

Sapi can be regarded as a road, a car It can run on different types of roads

And the execution of a php program means the car runs on the road.

Therefore, we need: an engine with excellent performance, a suitable wheel, a correct runway

The relationship between Apache and php

Apache’s analysis of php, It is accomplished through the php Module among many Modules.

To finally integrate php into the Apache system, you need to make some necessary settings for Apache. Here, we will take the mod_php5 SAPI operating mode of php as an example to explain. As for the concept of SAPI, we will explain it in detail later.

Assume that the versions we install are Apache2 and Php5, then you need to edit Apache’s main configuration file http.conf and add the following lines to it:

In Unix/Linux environment:

LoadModule php5_module modules/mod_php5.so

AddType application/x-httpd-php .php

Note: modules/mod_php5.so is mod_php5.so in the X system environment The location where the file is installed.

In Windows environment:

LoadModule php5_module d:/php/php5apache2.dll

AddType application/x-httpd-php .php

Note: Among them, d:/php/php5apache2.dll is the installation location of the php5apache2.dll file in the Windows environment.

These two configurations tell Apache Server that any Url user requests received in the future with php as the suffix need to call the php5_module module (mod_php5.so/php5apache2.dll) for processing.

Apache’s life cycle

Apache’s request processing process

Apache request Detailed explanation of processing loop
What are done in the 11 stages of Apache request processing loop?

1. Post-Read-Request stage

In the normal request processing process, this is the first stage where the module can insert hooks. This stage can be exploited for modules that want to get into processing requests very early.

2. URI Translation Phase
The main work of Apache in this phase: mapping the requested URL to the local file system. Modules can insert hooks at this stage to execute their own mapping logic. mod_alias uses this phase to work.

3. Header Parsing Phase
The main work of Apache in this phase: Check the header of the request. Since the module can perform the task of checking request headers at any point in the request processing flow, this hook is rarely used. mod_setenvif uses this phase to work.

4. Access Control Phase
The main work of Apache in this phase: Check whether access to the requested resource is allowed according to the configuration file. Apache's standard logic implements allow and deny directives. mod_authz_host uses this phase to work.

5. Authentication stage
The main work of Apache in this stage is to authenticate users according to the policies set in the configuration file and set the user name area. Modules can insert hooks at this stage to implement an authentication method.

6. Authorization stage
The main work of Apache in this stage is to check whether authenticated users are allowed to perform the requested operation according to the configuration file. The module can insert hooks at this stage to implement a user rights management method.

7. MIME Type Checking Phase
The main work of Apache in this phase is to determine the content processing function to be used based on the relevant rules of the MIME type of the requested resource. The standard modules mod_negotiation and mod_mime implement this hook.

8. FixUp stage
This is a general stage that allows the module to run any necessary processing before the content generator. Similar to Post_Read_Request, this is a hook that can capture any information and is also the most commonly used hook.

9. Response stage
The main work of Apache in this stage is to generate content returned to the client and be responsible for sending an appropriate reply to the client. This stage is the core part of the entire process.

10. Logging stage
The main work of Apache in this stage: recording the transaction after the reply has been sent to the client. Modules may modify or replace Apache's standard logging.

11. CleanUp Phase
The main work of Apache in this phase: clean up the environment left after the completion of this request transaction, such as the processing of files and directories or the closing of Socket, etc. This is the first time for Apache The final stage of request processing.

LAMP architecture:

Four layers from bottom to top:

①liunx belongs to the bottom layer of the operating system

②apache server, belongs to the secondary server, communicates with Linux and PHP

③php: belongs to the server-side programming language, and is associated with apache through the php_module module

④Mysql and other web services: belong to the application Service, associated with mysql through PHP's Extensions plug-in module

Android system architecture diagram

Compare lamp and Android's architecture diagram, it seems to be somewhat similar to lamp architecture, I I don’t understand Android, but it feels a bit similar. Experts can point out the differences. I would be very grateful.

From top to bottom:

Android architecture-- ------------Description--------LAMP architecture

1. Application--------Specific application------- -web application

2. Application framework----java-------------PHP language and library

3. System runtime library:-- --Virtual machine---------WEB server

⒋Linux kernel:---Operating system------L

in lamp architecture The relationship between the lamp and the inside of the computer

The CPU is the factory, the hard disk is the large warehouse, the memory is the regular transfer center, and the virtual memory is the temporary transfer center

Php language is compiled into machine language by zend , operating cpu

The operation of the database is an I/O operation and a mechanical movement. In other words, the bottleneck of a website is caused by reading and writing to the hard disk. The solution is to reduce the number of I/O operations. The use of buffering technology means that the data operations are placed in the mencache, and when it reaches a certain order of magnitude, it is written to the database at once. The mencache belongs to the key--value relationship

rather than relational data. It is also built based on this concept. , also belongs to the key--value relationship

Frequent read operations------Put it in mencache

Read more and write less----Put it in nosql----- -The reading function is very powerful!

The above is the entire content of this article. I hope it will be helpful to everyone's study. For more related content, please pay attention to the PHP Chinese website!

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