strict_argcount.php

<?php

interface Adapter
{
  public function init($required);
}
// Warning: caller will pass 2 argument
class NotOk implements Adapter
{
  public function init($required){}
}

// Ok: caller will pass 2 argument
class Ok implememts Adapter
{
  public function init($required, $optionnal = null){}
}

class Caller
{ 
  public function __construct(Adapter $adapter)
  {
    $adapter->init($this, __CLASS__);
  }
}