<?php
$x=TRUE;
$y=FALSE;
$z=$y OR $x;
?>
Is $z TRUE or FALSE?
In this case, $z will be FALSE because the above code is equivalent to <?php ($z=$y) OR $x ?> rather than <?php $z=($y OR $x) ?> as might be expected - because the OR operator has lower precedence than assignment operators.
On the other hand, after this code sequence:
<?php
$x=TRUE;
$y=FALSE;
$z=$y || $x;
?>
$z will be TRUE, as expected, because the || operator has higher precedence than assignment: The code is equivalent to $z=($y OR $x).
This is why you should NEVER use the OR operator without explicit parentheses around the expression where it is being used.
