Booleans
This is the simplest type. A bool expresses a truth value. It can be either true
or false
.
Syntax
To specify a bool literal, use the constants true
or false
. Both are case-insensitive.
<?php
$foo = True; // assign the value TRUE to $foo
?>
Typically, the result of an operator which returns a bool value is passed on to a control structure.
<?php
// == is an operator which tests
// equality and returns a boolean
if ($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 bool, 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 bool argument.
See also Type Juggling.
When converting to bool, the following values are considered false
:
- the boolean
false
itself - the integers 0 and -0 (zero)
- the floats 0.0 and -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
).
-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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Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/language.types.boolean.php