gistfile1.php

<?php

$a = 1;
$b = 2;
$c = 3;

$d = $c | $b;

if ($d & $a) {
   // This line is reached and it shouldn't be
}

$c = 4;

$d = $c | $b;

if ($d & $a) {
   // This line is correctly not reached
}