Booleans

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

????: 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.

// == 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 " \n"; } // ...because you can simply type if ($show_separators) { echo " \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 (PHP 4 only)

• the special type NULL (including unset variables)

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

?????

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

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) ?>