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.
To specify a boolean literal, use either the keyword TRUE or FALSE. Both are case-insensitive.
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"; } |
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)
an array with zero elements
an object with zero elements
the special type NULL
Warning |
-1 is considered TRUE, like any other non-zero (whether negative or positive) number! |