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
FALSE
itself - 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
).
-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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https://secure.php.net/manual/en/language.types.boolean.php