Logical Operators

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## 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"

    // 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)