function autoload($classname){
    // echo $classname;
    $class = $classname.".class.php";
    require($class);
}

// 注册自动加载函数
spl_autoload_register("autoload");

$oop = new Oop();
$oop->test();

$upload = new Upload();
$upload->test();

Oop.class.php

<?php
class Oop{
    function test(){
        echo "123";
    }
}

Upload.class.php

class Upload{
    function test(){
        echo "upload";
    }
}