ISP.php

<?php

interface FlyingCreature
{
    public function fly();
}

interface FeatheredCreature
{
    public function molt();
}

interface SwimmingCreature
{
    public function swim();
}

class Eagle implements FeatheredCreature, FlyingCreature
{
    public function fly()
    {
        // ...
    }

    public function molt()
    {
        // ...
    }
}

class Penguin implements FeatheredCreature, SwimmingCreature
{
    public function molt()
    {
        // ...
    }

    public function swim()
    {
        // ...
    }
}