Booleans
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 constants 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
FALSEitself
- the integer 0 (zero)
- the float 0.0 (zero)
- the empty string, and the string "0"
- an array with zero elements
- the special type NULL (including unset variables)
- SimpleXML objects created from empty tags
Every other value is considered TRUE (including any resource and NAN).
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)
?>
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