Description:
------------
When a parameter(declared as reference) is passed by mixing an expression & assignment, the paramter actually passed seems to be the expression, not the variable itself.

PHP version tested: 5.4.37 & 5.5.18.

Test script:
---------------
function test (&$a)
{
    $a = 10;
}
test ($a = 20);
echo $a;


Expected result:
----------------
10

Actual result:
--------------
20