How to implement automatic loading of classes in php

How to implement automatic class loading in php: 1. Use the "__autoload" magic function to load classes; 2. Use the "spl_autoload_register" function to replace the autoload function.

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class means that in the outside page, There is no need to "import" class files, but the program will dynamically load the required class files when needed.

Method 1: Use the __autoload magic function

When the program needs a certain class, it will call this function. This function we You need to define and write the general statements for loading class files yourself.

<?php
    //需要类是自动调用，而且会传进来一个类名，这个案例的文件名为21A.class.php,类名为A
     function __autoload($className){
      require "./21".$className.".class.php";
    }
    $o1 = new A();
    $o1->v1 = 10;
    echo "<br/>v1：".$o1->v1;
  ?>

Method 2: Use the spl_autoload_register function

The function of this function is to have more lives A function that can be used to replace the autoload function. The syntax is as follows: spl_autoload_regist("function name 1"); if spl_autoload_register is used, autoload will be invalid.

<?php
    //注册两个用于自动加载的函数名
    spl_autoload_register(&#39;auto1&#39;);
    spl_autoload_register(&#39;auto2&#39;);
    function auto1($className){
      $file = "./21".$className.".class.php";
      if(file_exists($file)){
        require "./21".$className.".class.php";
      }
    }
    function auto1($className){
      $file = "./22".$className.".class.php";
      if(file_exists($file)){
        require "./22".$className.".class.php";
      }
    }
    //如果需要一个类，但这个页面还没有记载，就会依次调用auto1和auto2,知道找到该类文件并加载
  ?>

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