How to implement php constructor that can accept different number of parameters?

How to implement php constructor that can accept different number of parameters?

Like

class Person {
    function __construct() { 
        // some fancy implementation
    } 
} 

$a = new Person('John');
$b = new Person('Jane', 'Doe');
$c = new Person('John', 'Doe', '25');

What is the best way to implement this in php?

Thanks, Milo

One solution is to use defaults:

public function __construct($name, $lastname = null, $age = 25) {
    $this->name = $name;
    if ($lastname !== null) {
        $this->lastname = $lastname;
    }
    if ($age !== null) {
        $this->age = $age;
    }
}

The second one is to accept array, associative array or object (example about associative array):

public function __construct($params = array()) {
    foreach ($params as $key => $value) {
        $this->{$key} = $value;
    }
}

But in the second case it should be passed like this:

$x = new Person(array('name' => 'John'));

The third option has been pointed by tandu:

Constructor arguments work just like any other function's arguments. Simply specify defaults php.net/manual/en/… or use func_get_args().

EDIT: Pasted here what I was able to retrieve from original answer by tandu (now: Explosion Pills).