Introduction
Integers
Types
PHP Manual

## Booleans

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

### Syntax

To specify a boolean literal, use the keywords `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 boolean 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 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`:

- 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)
- SimpleXML objects created from empty tags

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

Warning

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

`<?php
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)
?>`

Introduction
Integers
Types
PHP Manual