Description:
------------
<?php
class A { }
class B           {  public function m(A $a = NULL, &$n) { echo "B.m";} };
class C extends B {  public function m(  $a            ) { echo "C.m";} };
$b = new B();
$b->m(new A(), $b);
$c = new C();
$c->m(new A(), $b);
?>

reports:

PHP Warning:  Declaration of C::m($a) should be compatible with B::m(A $a, &$n) on line 4

but shall report:

PHP Warning:  Declaration of C::m($a) should be compatible with B::m(A $a = NULL, &$n) on line 4

The same happens with php 5.6.17 .

Just removing &$n leads to the correct "PHP Warning:  Declaration of C::m($a) should be compatible with B::m(A $a = NULL) on line 4"