Description:
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It seems that documentation is not clear about references. 

There is no mentioning about `assign by ref` operator(http://php.net/manual/en/language.operators.precedence.php). And its precedence is higher than `instanceof`. 

Also, there is exists mentioning of `left | & | bitwise and references`. What is a meaning of `references` in this line?

Test script:
---------------
$a = &$b instanceof stdClass;
$c =  $d instanceof stdClass;

// line     # *  op                   fetch          ext  return  operands
// -------------------------------------------------------------------------
//    3     0  >   ASSIGN_REF                               $0      !0, !1
//          1      FETCH_CLASS                          84  :1      'stdClass'
//          2      INSTANCEOF                               ~2      $0, $1
//          3      FREE                                             ~2
//    4     4      FETCH_CLASS                          84  :3      'stdClass'
//          5      INSTANCEOF                               ~4      !3, $3
//          6      ASSIGN                                           !2, ~4
//          7    > RETURN                                           1