Booleans

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- Booleans

## Booleans

The bool type only has two values, and is used to express a truth value. It can be either `true` or `false`.

### Syntax

To specify a bool literal, use the constants `true` or `false`. Both are case-insensitive.

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

Typically, the result of an operator which returns a bool value is passed on to a control structure.

    <?php
    // == is an operator which tests
    // 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 this can be used with exactly the same meaning:
    if ($show_separators) {
        echo "<hr>\n";
    }
    ?>

### Converting to boolean

To explicitly convert a value to bool, use the `(bool)` cast. Generally this is not necessary because when a value is used in a logical context it will be automatically interpreted as a value of type bool. For more information see the Type Juggling page.

When converting to bool, the following values are considered `false`:

- the boolean `false` itself
- the integer `0` (zero)
- the floats `0.0` and `-0.0` (zero)
- the empty string `""`, and the string `"0"`
- an array with zero elements
- the unit type NULL (including unset variables)
- Internal objects that overload their casting behaviour to bool. For example: SimpleXML objects created from empty elements without attributes.

Every other value is considered `true` (including resource and `NAN`).

Warning

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

Example #1 Casting to Boolean

    <?php
    var_dump((bool) "");        // bool(false)
    var_dump((bool) "0");       // 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)
    ?>