Constructor Overloading in PHP

Problem Approch

I have a class like this with a overloaded constructors

Code

<?php 
/*
  Users Abstract Class

*/
abstract class User 
{

    protected $user_email;
    protected $user_username;
    protected $user_password;
    protected $registred_date;


    //Default constructor
    function User()
    {

    }

    //overloded constructor
    function User($input_username,$input_email,$input_password)
    {
    __set($this->user_username,$input_username);
    __set($this->user_email,$user_password);
    __set($this->user_password,$input_password);
    }

}


?>

Problem Details

Above code provides an error : error:Fatal error: Cannot redeclare User::User()

As other languages such as C++ and Java uses the above approach to overload the constructors how to do it in PHP OOP ?

Additional Information

Im using *PHP 5.3.2 in LAMP * which OOP concepts should fully supported in this version