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 operator which returns a boolean
    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:

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

Warning

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