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"// The result of the expression (false || true) is assigned to $e// Acts like: ($e = (false || true))$e = false || true;// The constant false is assigned to $f before the "or" operation occurs// Acts like: (($f = false) or true)$f = false or true;var_dump($e, $f);// --------------------// "&&" has a greater precedence than "and"// The result of the expression (true && false) is assigned to $g// Acts like: ($g = (true && false))$g = true && false;// The constant true is assigned to $h before the "and" operation occurs// Acts like: (($h = true) and false)$h = true and false;var_dump($g, $h);?>
The above example will output something similar to:
bool(true) bool(false) bool(false) bool(true)