signature

signatures.php

<?php
class Parents
{
    public function doSomething($x)
    {
        print $x;
    }
}

class ChildA extends Parents
{
    public function doSomething($x)
    {
        print_r (func_get_args());
    }
}

class ChildB extends Parents
{
    public function doSomething($x, $y)
    {
        print_r (func_get_args());
    }
}

$child = new ChildA;
$child->doSomething('x', 'y');
$child->doSomething();

interface BazInterface
{
    public function doSomething($x);
}

class BazA implements BazInterface
{
    public function doSomething()
    {
    }
}

class BazB implements BazInterface
{
    public function doSomething($x, $y)
    {
    }
}