PHP: Logical Operators

Logical Operators

**Logical Operators**
Example	Name	Result
$a and $b	And	`TRUE` if both $a and $b are `TRUE`.
$a or $b	Or	`TRUE` if either $a or $b is `TRUE`.
$a xor $b	Xor	`TRUE` if either $a or $b is `TRUE`, but not both.
! $a	Not	`TRUE` if $a is not `TRUE`.
$a && $b	And	`TRUE` if both $a and $b are `TRUE`.
$a \|\| $b	Or	`TRUE` if either $a or $b is `TRUE`.

The reason for the two different variations of "and" and "or" operators is that they operate at different precedences. (See Operator Precedence.)

Example #1 Logical operators illustrated


<?php



// foo() will never get called as those operators are short-circuit

$a = (false && foo());

$b = (true  || foo());

$c = (false and foo());

$d = (true  or  foo());



// "||" has a greater precedence than "or"

$e = false || true; // $e will be assigned to (false || true) which is true

$f = false or true; // $f will be assigned to false

var_dump($e, $f);



// "&&" has a greater precedence than "and"

$g = true && false; // $g will be assigned to (true && false) which is false

$h = true and false; // $h will be assigned to true

var_dump($g, $h);

?>

The above example will output something similar to:

bool(true)
bool(false)
bool(false)
bool(true)