Method overloading and class inheritance

I cannot get understanding code to work? I dont know why? Is it even possible?

I want always to call a default class and there methods. But actually depending on the parameter givven. I want to load methods from that specifiec customer?

<?php
#System Defaults
namespace DefaultNameSpace;

class defaultClass{

    private $property;

    public function __construct($cusotmer)
    {
        if (isset($cusotmer)开发者_运维问答){
            $namespace = '\Customer' . $cusotmer .'Namespace\defaultClass';
            # create new dynamic object
            return new $namespace();
        } else {
            return $this;
        }

    }
    public function printInvoice(){
        echo 'Default Print';
    }
    public function createInvoice($invoice){}
}

#Customer One defaults
namespace CustomerOneNamespace;

class defaultClass extends \DefaultNameSpace\defaultClass {

    private $property;

    public function __construct()
    {
        return $this;
    }
    public function printInvoice(){
        echo 'Customer One';
    }
    public function createInvoice ($invoice){
        echo 'Create invoice Customer One '.$invoice;
    }
}
# Customer Two Defaults
namespace CustomerTwoNamespace;

class defaultClass extends \DefaultNameSpace\defaultClass {

    private $property;

    public function __construct()
    {
        return $this;
    }
    public function printInvoice(){
        echo 'Customer Two';
    }
}
# Call alsways default Class
$test = new \DefaultNameSpace\defaultClass('Two');
$test->printInvoice();
$test->createInvoice('123456');

?>

You can't create an object of descendatnt class when calling ancestor class' constructor, so this code will not work as you want.

$test = new \DefaultNameSpace\defaultClass('Two'); 

To achieve what you want you could use Factory pattern. Simplified (and very primitive) example:

function factoryMethod($type){
    $result = null;
    switch($type){
        case 1:
            $result = new Class1();
            break;
        case 2:
            $result = new Class2();
            break;
        default:
            $result = new ClassDefault();
            break;
    }
    return $result;
}

$obj = factoryMethod(2);
$obj->printInvoice();

Note that you are completely responsible for returning from factoryMethod objects that implement required interface, as PHP do not support return type hinting (as far as I know).