PHP Handleiding
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# Booleans

This is the easiest type. A boolean expresses a truth value. It can be either `TRUE` or `FALSE`.

> Opmerking: The boolean type was introduced in PHP 4.

## Syntax

To specify a boolean literal, use either the keyword `TRUE` or `FALSE`. Both are case-insensitive.

`<?php $foo = True; // assign the value TRUE to $foo ?>`

Usually you use some kind of operator which returns a boolean value, and then pass it on to a control structure.

`<?php // == is an operator which test // equality and returns a boolean if ($action == "show_version") { echo "The version is 1.23"; } // this is not necessary... if ($show_separators == TRUE) { echo "<hr>\n"; } // ...because you can simply type if ($show_separators) { echo "<hr>\n"; } ?>`

## Converting to boolean

To explicitly convert a value to boolean, use either the (bool) or the (boolean) cast. However, in most cases you do not need to use the cast, since a value will be automatically converted if an operator, function or control structure requires a boolean argument.

See also Type Juggling.

When converting to boolean, the following values are considered `FALSE`:

- the boolean `FALSE` itself

- the integer 0 (zero)

- the float 0.0 (zero)

- the empty string, and the string "0"

- an array with zero elements

- an object with zero member variables

- the special type NULL (including unset variables)

Every other value is considered `TRUE` (including any resource).

Waarschuwing
-1 is considered `TRUE`, like any other non-zero (whether negative or positive) number!

`<?php var_dump((bool) ""); // bool(false) var_dump((bool) 1); // bool(true) var_dump((bool) -2); // bool(true) var_dump((bool) "foo"); // bool(true) var_dump((bool) 2.3e5); // bool(true) var_dump((bool) array(12)); // bool(true) var_dump((bool) array()); // bool(false) var_dump((bool) "false"); // bool(true) ?>`

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