class A

{

    function __construct()

    {

        $a = func_get_args();

        $i = func_num_args();

        if (method_exists($this,$f='__construct'.$i)) {

            call_user_func_array(array($this,$f),$a);

        }

    } 

    function __construct1($a1)

    {

        echo('__construct with 1 param called: '.$a1.PHP_EOL);

    } 

    function __construct2($a1,$a2)

    {

        echo('__construct with 2 params called: '.$a1.','.$a2.PHP_EOL);

    } 

    function __construct3($a1,$a2,$a3)

    {

        echo('__construct with 3 params called: '.$a1.','.$a2.','.$a3.PHP_EOL);

    }

}

$o = new A('sheep');

$o = new A('sheep','cat');

$o = new A('sheep','cat','dog');