Call forwarding with interfaces and argument unpacking and the splat operator.

example.php

<?php

interface SomeInterface
{
    public function forwardedCall($argument);
}

class Pre56BreakingInterface implements SomeInterface
{
    public function forwardedCall()
    {
        $arguments = func_get_args();
        $subject = $this->getSubject();

        return call_user_func_array([$subject, 'forwardedCall'], $arguments);
    }
}

class Pre56ImplementingInterface implements SomeInterface
{
    public function forwardedCall($argument)
    {
        // $argument is dead code
        $arguments = func_get_args();
        $subject = $this->getSubject();

        return call_user_func_array([$subject, 'forwardedCall'], $arguments);
    }
}

class ModernPHPImplementation implements SomeInterface
{
    public function forwardedCall($argument, ...$trailing)
    {
        // YAY no dead code.
        $subject = $this->getSubject();

        return $subject->forwardedCall($argument, ...$trailing);
    }
}