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


To specify a boolean literal, use the constants TRUE or FALSE. Both are case-insensitive.

$foo = True; // assign the value TRUE to $foo

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

// == 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 boolean, use the (bool) or (boolean) casts. However, in most cases the cast is unnecessary, 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 and NAN).


-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)

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