Detailed explanation of the underlying operating mechanism and working principles of PHP

I recently set up a server, and suddenly I felt how the lamps work, or how they are connected? I usually just write programs, and I have never thought about the working principle between them:

The underlying working principle of PHP

Related learning recommendations: PHP programming from entry to proficiency

Figure 1 PHP structure

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

①Zend engine

Zend is implemented in pure C and is the core part of PHP. It translates PHP code (lexical, syntax analysis, etc.) Process) 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. It is the core of everything. 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 is a car, then
the framework of the car It is php itself
Zend is the engine (engine) of the car
The various components below Ext are the wheels of the car
Sapi can be regarded as a road, and the car can run on different types of roads
The execution of a php program is like a car running on the road.
Therefore, we need: Excellent performance engine, suitable wheels, correct runway

The relationship between Apache and php

Apache for php The analysis is completed 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 the installation location of the mod_php5.so file in the X system environment.

In Windows environment:

LoadModule php5_module d:/php/php5apache2.dll
AddType application/x-httpd-php .php

Note: d:/php/php5apache2.dll is the installation location of the php5apache2.dll file in 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

Detailed explanation of the Apache request processing cycle

The 11 stages of the Apache request processing cycle have been completed What things?

1. Post-Read-Request phase

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

2. URI Translation stage

Apache’s main job in this stage: 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 stage
Apache’s main work in this stage: 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 resources 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: authenticate users according to the policy 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 phase
The main work of Apache in this phase: 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 stage
The main work of Apache in this stage: determine the content processing function to be used according to 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
Apache’s main job 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 phase
The main work of Apache in this phase: recording transactions 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 application services and are associated with mysql through PHP's Extensions plug-in module

Android system architecture diagram

Lamp and Android architecture Comparing the pictures, it seems to be somewhat similar to the lamp architecture. I don't know Android, but it feels a bit similar. Experts can point out the differences. I would be very grateful.

From top to bottom Next:

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-------Lamp architecture The relationship between the L

lamp and the inside of the computer

The CPU is the factory, the hard disk is the large warehouse, and the memory is the regular transfer center , virtual memory is a 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, that is to say, the operation of a website The bottleneck is caused by the reading and writing of the hard disk. The solution is to reduce the number of I/O operations and use buffering technology. That is, the data operations are placed in the mencache. When it reaches a certain order of magnitude, it is written to the database at once. The mencache belongs to the key. --value relationship

Non-relational data is also built based on this concept, and also belongs to 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!

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