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Today, I will talk to you about the use and principle of autoload automatic loading mechanism in PHP, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.

PHPautoload automatic loading mechanism can reduce unnecessary file inclusion, so as to improve the performance of PHP websites to a certain extent. The following editor will explain how to use the autoload automatic loading mechanism in PHP? what are the principles of the autoload automatic loading mechanism in PHP?

What are the methods of using autoload automatic loading mechanism in PHP

Usage of _ _ autoload 1

The most commonly used method is to find out the class file according to the class name, and then require_one

Function__autoload ($class_name) {

$path=str_replace ('_','/', $class_name)

Require_once$path.'.php'

}

/ / the Http/File/Interface.php file will be loaded automatically here

$a=newHttp_File_Interface ()

The advantage of this method is that it is easy to use. Of course, there is also a disadvantage, the disadvantage is that the class name and file path are forced to do a convention, when modifying the file structure, it is necessary to modify the class name.

Usage of _ _ autoload 2 (direct mapping method)

$map=array (

'Http_File_Interface'= >' CureGrane PHP, PHP, HTTP, PHP, File, Interface.php'

)

Function__autoload ($class_name) {

If (isset ($map [$class_name])) {

Require_once$map [$class_name]

}

}

/ / the C:/PHP/HTTP/FILE/Interface.php file will be loaded automatically here

$a=newHttp_File_Interface ()

The advantage of this method is that the class name and file path are only maintained by a mapping, so when the file structure changes, there is no need to change the class name, just modify the corresponding items in the mapping.

The disadvantage of this approach over the previous approach is that the mapping is very troublesome to maintain when there are too many files, so you may consider using json or a single file for maintenance. You may want to use a framework to maintain or establish such a mapping.

What are the principles of autoload automatic loading mechanism in PHP?

Spl_autoload

The biggest drawback of _ _ autoload is that it cannot have multiple autoload methods

Well, consider the following scenario where your project references a project of someone else's, your project has a _ _ autoload in your project, and someone else's project has a _ _ autoload, so the two _ _ autoload conflict. The solution is to modify _ _ autoload to become one, which is undoubtedly very tedious.

So we urgently need to use an autoload call stack so that spl's autoload series of functions appear. You can use spl_autoload_register to register multiple custom autoload functions

If your PHP version is greater than 5.1, you can use spl_autoload.

Spl_autoload, the default implementation of _ autoload (), looks for $class_name (.php / .inc) in include_path.

Spl_autoload implements automatic loading:

/ * http.php*/

Classhttp

{

Publicfunctioncallname () {

Echo "thisishttp"

}

}

/ * test.php*/

Set_include_path ("/ home/yejianfeng/handcode/"); / / you need to put the path into include here.

Spl_autoload ("http"); / / find / home/yejianfeng/handcode/http.php

$a=newhttp ()

$a-> callname ()

Spl_autoload_register

Register the function in the SPL__autoload function stack and look directly at an example:

/ * http.php*/

Classhttp

{

Publicfunctioncallname () {

Echo "thisishttp"

}

}

/ * test.php*/

Spl_autoload_register (function ($class) {

If ($class=='http') {

Require_once ("/ home/yejianfeng/handcode/http.php")

}

})

$a=newhttp ()

$a-> callname ()

Spl_autoload_call

To call the calling function registered in spl_autoload_register, see the following example

/ * http.php*/

Classhttp

{

Publicfunctioncallname () {

Echo "thisishttp"

}

}

/ * http2.php*/

Classhttp

{

Publicfunctioncallname () {

Echo "thisishttp2"

}

}

/ * test.php*/

Spl_autoload_register (function ($class) {

If ($class=='http') {

Require_once ("/ home/yejianfeng/handcode/http.php")

}

If ($class=='http2') {

Require_once ("/ home/yejianfeng/handcode/http2.php")

}

})

Spl_auto_call ('http2')

$a=newhttp ()

$a-> callname (); / / output "thisishttp2" at this time

The function spl_auto_register makes it possible to use custom functions for automatic loading instead of using _ _ autoload. This method is often used now.

This approach is used by Zend's AutoLoader module. Extract the corresponding code

Spl_autoload_register (array (_ _ CLASS__,'autoload'))

Publicstaticfunctionautoload ($class)

{

... ..

} .

After reading the above, do you have any further understanding of the use and principle of autoload autoloading mechanism in PHP? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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