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Logical Operators

Table 6.7. Logical Operators

ExampleNameResult
$a and $bAndTRUE if both $a and $b are TRUE.
$a or $bOrTRUE if either $a or $b is TRUE.
$a xor $bXorTRUE if either $a or $b is TRUE, but not both.
! $aNotTRUE if $a is not TRUE.
$a && $bAndTRUE if both $a and $b are TRUE.
$a || $bOrTRUE 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 6.6. 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)