Use the SPL spl_autoload_register and _ autoload methods in php

In php, The spl_autoload_register and _ autoload methods are only available in php5. Next I will introduce you to the usage of these two magic functions.

The spl_autoload_register () function should be one of the most used and very core functions in mainstream frameworks. It can automatically register functions and classes and implement functions similar to the _ autoload () function, it simplifies class calling and loading, and improves work efficiency.

Supported versions: PHP 5> = 5.1.2

Efficiency issues. The php manual says this:

Bool spl_autoload_register ([callback $ autoload_function])

Register the function to the SPL _ autoload function stack. If the functions in the stack are not activated, activate them. If the _ autoload function has been implemented in your program, it must be explicitly registered to the _ autoload stack. Because the spl_autoload_register () function replaces the _ autoload function in Zend Engine with spl_autoload () or spl_autoload_call ().

Spl_autoload_register
(PHP 5> = 5.1.2)
Spl_autoload_register-register _ autoload () function
Description
Bool spl_autoload_register ([callback $ autoload_function])
Register the function to the SPL _ autoload function stack. If the functions in the stack are not activated, activate them.
If the _ autoload function has been implemented in your program, it must be explicitly registered to the _ autoload stack. Because
The spl_autoload_register () function replaces the _ autoload function in Zend Engine with spl_autoload () or
Spl_autoload_call ().
Parameters
Autoload_function
The automatically loaded function to be registered. If no parameter is provided, the default function of autoload is automatically registered.
Spl_autoload ().
Return Value
If the call succeeds, TRUE is returned. If the call fails, FALSE is returned.
Note: SPL is the abbreviation of Standard PHP Library (Standard PHP Library. It is an extension library introduced by PHP5. Its main functions include the implementation of the autoload mechanism and various Iterator interfaces or classes. The implementation of the SPL autoload mechanism is achieved by pointing the function pointer autoload_func to the self-implemented function with the automatic loading function. SPL has two different functions: spl_autoload and spl_autoload_call. Different automatic loading mechanisms are implemented by pointing autoload_func to these two function addresses.

The Code is as follows:

Copy code

Class autoload { Public static function load ($ class name) { $ Filename = $ classname. ". class. php "; If (file_exists ($ filename )){ Require_once $ filename; } } }   Function _ autoload ($ class name) { // This is the default autoload method. $ Filename = $ classname. ". class. php "; If (file_exists ($ filename )){ Require_once $ filename; } }   // Register an autoloader Spl_autoload_register ('autoload: load '); Spl_autoload_register ('_ autoload '); // Note: The following classes do not seem to be defined, but the system will automatically search for them based on the path provided by SQL _autoload_register. // Foo. class. php file. If it is not found, an error is returned. $ Foo = new foo (); $ Foo-> bar (); ?>

In addition:

The _ autoload method will expire after spl_autoload_register, because the autoload_func function pointer has pointed to the spl_autoload Method
* You can add the _ autoload method to the autoload_functions list using the following method:

Spl_autoload_register ('_ autoload ');

In addition, we can use our custom loading method:

The first function:

The Code is as follows:	Copy code
Function my_own_loader ($ classname) { $ Class_file = strtolower ($ classname). ". php "; If (file_exists ($ class_file )){ Require_once ($ class_file ); } }   Spl_autoload_register ("my_own_loader ");   $ A = new ();

Type 2:

The Code is as follows:	Copy code
Class Loader { Public static function my_own_loader ($ classname) { $ Class_file = strtolower ($ classname). ". php "; If (file_exists ($ class_file )){ Require_once ($ class_file ); } } }   // Pass the class and method names in the form of Arrays Spl_autoload_register (array ("Loader", "my_own_loader ")); $ A = new ();

Instance: When the CI framework loads classes, the corresponding model is also generated.

The Code is as follows:

Copy code

Static public function myAutoload ($ class ){ If (file_exists (APPPATH. 'models'. DIRECATORY_SEPARATOR. $ class. '. php ')){ Require_once APPPATH. 'models'. DIRECATORY_SEPARATOR. $ class. '. php '; } } /** * Register the loader */ Static public function autoload (){ Spl_autoload_register (array (_ CLASS __, 'myautoload ')); If (class_exists ('_ autoload ')){ Spl_autoload_register ('_ autoload '); } } MY_Controller: autoload ();

Of course, the above is just the simplest example, __autoload just goes to include_path to find the class file and load it. we can define the _ autoload loading class rules as needed.

In addition, we can use spl_autoload_register to register our own autoload function if we do not want to call _ autoload when loading automatically, but call our own function (or class method. Its function prototype is as follows:
Bool spl_autoload_register ([callback $ autoload_function])

We will continue to rewrite the example above:

The Code is as follows:	Copy code
View plaincopy to clipboardprint? Function loader ($ class) { $ File = $ class. '. php '; If (is_file ($ file )){ Require_once ($ file ); } } Spl_autoload_register ('loader '); $ A = new (); Function loader ($ class) { $ File = $ class. '. php '; If (is_file ($ file )){ Require_once ($ file ); } } Spl_autoload_register ('loader '); $ A = new ();

This way, php can run normally. At this time, when looking for classes, php does not call _ autoload, but calls our own function loader. In the same way, the following statements can also be used:

The Code is as follows:	Copy code
View plaincopy to clipboardprint? Class Loader { Public static function loadClass ($ class) { $ File = $ class. '. php '; If (is_file ($ file )){ Require_once ($ file ); } } } Spl_autoload_register (array ('loader ', 'loadclass ')); $ A = new ();