Detailed explanation on the usage of spl_autoload_register() function in PHP

This article mainly introduces the usage of spl_autoload_register() function in PHP, and analyzes the related usage skills of __autoload function and spl_autoload_register function in the form of examples. Friends in need can refer to the

Recommended Manual : php Complete Self-Study Manual

Before understanding this function, let’s look at another function: __autoload.

1. __autoload

This is an automatic loading function. In PHP5, when we instantiate an undefined class, this will be triggered. function. Look at the following example:

printit.class.php:

<?php
class PRINTIT {
 function doPrint() {
 echo &#39;hello world&#39;;
 }
}
?>

index.php

<?
function __autoload( $class ) {
 $file = $class . &#39;.class.php&#39;;
 if ( is_file($file) ) {
 require_once($file);
 }
}
$obj = new PRINTIT();
$obj->doPrint();?>

After running index.php, hello world is output normally. In index.php, since printit.class.php is not included, when instantiating printit, the __autoload function is automatically called. The value of the parameter $class is the class name printit. At this time, printit.class.php is introduced. .

This method is often used in object-oriented, which can avoid writing too many reference files and also make the entire system more flexible.

2. spl_autoload_register()

Look at spl_autoload_register() again. This function has the same effect as __autoload. Let’s look at a simple example:

<?
function loadprint( $class ) {
 $file = $class . &#39;.class.php&#39;;
 if (is_file($file)) {
 require_once($file);
 }
}
spl_autoload_register( &#39;loadprint&#39; );
$obj = new PRINTIT();
$obj->doPrint();?>

Replace __autoload with the loadprint function. But loadprint will not be triggered automatically like __autoload. At this time, spl_autoload_register() will work. It tells PHP to execute loadprint() when it encounters an undefined class.

spl_autoload_register() calls the static method

<?
class test {
 public static function loadprint( $class ) {
 $file = $class . &#39;.class.php&#39;;
 if (is_file($file)) {
  require_once($file);
 }
 }
}
spl_autoload_register( array(&#39;test&#39;,&#39;loadprint&#39;) );
//另一种写法：spl_autoload_register( "test::loadprint" );
$obj = new PRINTIT();
$obj->doPrint();?>

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 into the SPL __autoload function stack. Activate functions in this stack if they are not already active.

If the __autoload function has been implemented in your program, it must be explicitly registered in the __autoload stack. Because the spl_autoload_register() function will replace the __autoload function in Zend Engine with spl_autoload() or spl_autoload_call().

Parameters

autoload_function

The autoload function to be registered. If no parameters are provided, the default implementation function spl_autoload() of autoload is automatically registered.

Return value

Returns TRUE if successful and FALSE if failed.

Note:

SPL is the abbreviation of Standard PHP Library. It is an extension library introduced in PHP5. Its main functions include the implementation of the autoload mechanism and various Iterator interfaces or classes. The SPL autoload mechanism is implemented by pointing the function pointer autoload_func to a self-implemented function with autoloading 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 different function addresses.

classLOAD
{
 staticfunctionloadClass($class_name)
  {
    $filename= $class_name.".class.php";
 $path= "include/".$filename
    if(is_file($path)) returninclude$path;
  }
}
/**
 * 设置对象的自动载入
 * spl_autoload_register — Register given function as __autoload() implementation
 */
spl_autoload_register(array('LOAD', 'loadClass'));
/**
*__autoload 方法在 spl_autoload_register 后会失效，因为 autoload_func 函数指针已指向 spl_autoload 方法
* 可以通过下面的方法来把 _autoload 方法加入 autoload_functions list
*/
spl_autoload_register( '__autoload');

If you use spl_autoload_register to register a class method and __autoload function at the same time, then according to the order of registration, if the class file is loaded in the first registered method or function, it will not be loaded again. Execute the method or function of the second registered class. Otherwise, the method or function of the second registered class will be executed.

<?php
class autoloader {
  public static $loader;
  public static function init() {
    if (self::$loader == NULL)
      self::$loader = new self ();
    return self::$loader;
  }
  public function __construct() {
    spl_autoload_register ( array ($this, &#39;model&#39; ) );
    spl_autoload_register ( array ($this, &#39;helper&#39; ) );
    spl_autoload_register ( array ($this, &#39;controller&#39; ) );
    spl_autoload_register ( array ($this, &#39;library&#39; ) );
  }
  public function library($class) {
    set_include_path ( get_include_path () . PATH_SEPARATOR . &#39;/lib/&#39; );
    spl_autoload_extensions ( &#39;.library.php&#39; );
    spl_autoload ( $class );
  }
  public function controller($class) {
    $class = preg_replace ( &#39;/_controller$/ui&#39;, &#39;&#39;, $class );
    set_include_path ( get_include_path () . PATH_SEPARATOR . &#39;/controller/&#39; );
    spl_autoload_extensions ( &#39;.controller.php&#39; );
    spl_autoload ( $class );
  }
  public function model($class) {
    $class = preg_replace ( &#39;/_model$/ui&#39;, &#39;&#39;, $class );
    set_include_path ( get_include_path () . PATH_SEPARATOR . &#39;/model/&#39; );
    spl_autoload_extensions ( &#39;.model.php&#39; );
    spl_autoload ( $class );
  }
  public function helper($class) {
    $class = preg_replace ( &#39;/_helper$/ui&#39;, &#39;&#39;, $class );
    set_include_path ( get_include_path () . PATH_SEPARATOR . &#39;/helper/&#39; );
    spl_autoload_extensions ( &#39;.helper.php&#39; );
    spl_autoload ( $class );
  }
}
//call
autoloader::init ();
?>

Summary: The above is the entire content of this article, I hope it will be helpful to everyone's study.

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