Description:
------------
I am trying to adjst some code to E_STRICT standards but I am getting a "Signature mismatch during inheritance" error, when it seems that there sould be none.

What is more bizarre is that this error only occurs when I am trying to implement SomeInterface in the extendig class.

Test script:
---------------
interface SomeInterface
{
}

abstract class FooClass
{
}

abstract class FooBarClass extends FooClass
{
}

abstract class LightAbstract
{
    public function returnArgument(FooClass $arg)
    {
        return $arg;
    }
}

// OK
class RedLight extends LightAbstract
{
    public function returnArgument(FooBarClass $arg)
    {
        return parent::returnArgument($arg);
    }
}

// Outputs an error (E_STRICT)
class BlueLight extends LightAbstract implements SomeInterface
{
    public function returnArgument(FooBarClass $arg)
    {
        return parent::returnArgument($arg);
    }
}