Php/docs/language.types.boolean

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• Types
• Booleans

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 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";}?>

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).

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

<?phpvar_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)?>