The bool type only has two values, and is used to express
a truth value. It can be either true
or false
.
To specify a bool literal, use the constants true
or
false
. Both are case-insensitive.
<?php$foo = True; // assign the value TRUE to $foo?>
Typically, the result of an operator which returns a bool value is passed on to a control structure.
<?php// == is an operator which tests// equality and returns a booleanif ($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";}?>
To explicitly convert a value to bool, use the
(bool)
cast. Generally this is not necessary because when
a value is used in a logical context it will be automatically interpreted
as a value of type bool. For more information see the
Type Juggling page.
When converting to bool, the following values are considered
false
:
false
itself
0
(zero)
0.0
and -0.0
(zero)
""
,
and the string "0"
Every other value is considered true
(including resource
and NAN
).
-1
is considered true
, like any other non-zero
(whether negative or positive) number!
<?phpvar_dump((bool) ""); // bool(false)var_dump((bool) "0"); // 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)?>