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# Booleans

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

> Note: 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.

    $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.

    if ($action == "show_version") { // == is an <link linkend="language.operators">operator</link> which returns a <type>boolean</type>
        echo "The version is 1.23";
    }

    // this is not necessary:
    if ($show_separators == true) {
        echo "<hr>\n";
    }

    // because you can simply type this:
    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`

- 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 elements

- the special type NULL (including unset variables)

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

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

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