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PHP : Language Reference : Operators : Logical Operators

Logical Operators

Table 6.7. 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 6.6. Logical operators illustrated

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<?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:

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bool(true)

bool(false)

bool(false)

bool(true)

Code Examples / Notes » language.operators.logical

looris

Please note that while you can do things like: <?php your_function() or die("horribly"); ?> you can't do: <?php your_function() or return "whatever"; ?> (it will give you a syntax error).

lawrence

Note that PHP's boolean operators *always* return a boolean value... as opposed to other languages that return the value of the last evaluated expression. For example: $a = 0 || 'avacado'; print "A: $a\n"; will print: A: 1 in PHP -- as opposed to printing "A: avacado" as it would in a language like Perl or JavaScript. This means you can't use the '||' operator to set a default value: $a = $fruit || 'apple'; instead, you have to use the '?:' operator: $a = ($fruit ? $fruit : 'apple');

eduardofleury

;;;;;;;;;;;;;;;;;;;;;;;;; ; P1 P2; And; OR ; XOR ; ;;;;;;;;;;;;;;;;;;;;;;;;; ; V V ; V ; V ; F ; ; V F ; F ; V ; V ; ; F V ; F ; V ; V ; ; F F ; F ; F ; F ; ;;;;;;;;;;;;;;;;;;;;;;;;; <?php $a = 2; $b = 3; $c = 6; print !($a > $b && $b < $c);// true print (($a > $b) and ($b < $c));// false print ($a == $b or $b < $c); // true print $a == $b || $b < $c; // true $x = $a < $b; //$x = true $y = $b === $c; //$y = false print $x xor $y; // true ?>

andrew

> <?php > your_function() or return "whatever"; > ?> doesn't work because return is not an expression, it's a statement. if return was a function it'd work fine. :/

peter dot kutak

$test = true and false; ---> $test === true $test = (true and false); ---> $test === false $test = true && false; ---> $test === false

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Operator Precedence
Arithmetic Operators
Assignment Operators
Bitwise Operators
Comparison Operators
Error Control Operators
Execution Operators
Incrementing/Decrementing Operators
Logical Operators
String Operators
Array Operators
Type Operators

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