autoload

autoload.php

<?php
    
    // Your custom class dir
    define('CLASS_DIR', 'classe/');

    // Add your class dir to include path
    set_include_path(get_include_path().PATH_SEPARATOR.CLASS_DIR);

    // You can use this trick to make autoloader look for commonly used "My.class.php" type filenames
    spl_autoload_extensions('.php');
 

    // Use default autoload implementation
    spl_autoload_register();

index.php

<?php

include 'autoload.php';

use classe\Usuario;

$u = new Usuario;
var_dump($u);

Usuario.php

<?php

// dir classe/Usuario

namespace classe;

class Usuario
{
    private $email;
    private $senha;
	
    public function setEmail($email)
    {
       $email = strtolower($email);
       
       if(!filter_var($email, FILTER_VALIDATE_EMAIL))
        return false;
       else	
         $this->email = $email;
    }
    public function getEmail()
    {
    	return $this->email;
    }

 }