<?php
class LeClass
{
    public $name;
    public $surname;
    public $email;

}

class LeTestClass
{
    public function leFun($obj)
    {
        foreach ($obj as $property => $value) {
        	//var_dump($property);
            switch ($property) {
                case "name":
                case "surname":
                    $obj->$property = 'Василий';
                    //var_dump($obj->$property);
                    break;
                case 'email':
                	$obj->$property = 'Иван';
                	break;
                //default:
                //	$obj->$property = 'Иван';
            }
            var_dump($obj->$property);
        }
    }
}

$test = new LeTestClass;
$obj = new LeClass;
$test->leFun($obj);
var_dump($obj);