Operators
PHP Manual

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)

Operators
PHP Manual