php注意问题

<?php
class a{
    public function c($id){
        echo $id;
    }
}
class b extends a{
    public function c($id,$ic){
        parent::c($id);
        echo $ic;
    }
}
$b=new b();
$b->c(1,2);
/*interface d{
    public function e($id);
}
class f implements  d{
    public function e($id,$ic){//这里错误
        
    }
}
$d=new d();
$d->e(1,2);*/
/*abstract class g{
    public abstract function h($id);
}
class i extends g{
    public function h($id,$ic){//错误
        
    } 
}
$i= new i();
$i->h(1,2);*/