Booleans Syntax:
This is the easiest type. A boolean expresses a truth value. It can be either TRUE or FALSE.
Note:
The boolean type was introduced in PHP 4. Syntax
To specify a boolean literal, use either the keyword TRUE or FALSE. Both are case-insensitive.
<?php
$foo = True; // assign the value TRUE to $foo
?>
$foo = True; // assign the value TRUE to $foo
?>
Usually you use some kind of operator which returns a boolean value, and then pass it on to a control structure.
<?php
// == is an operator which test
// equality and returns a boolean
if ($action == "show_version") {
echo "The version is 1.23";
}
// this is not necessary...
if ($show_separators == TRUE) {
echo "<hr>\n";
}
// ...because you can simply type
if ($show_separators) {
echo "<hr>\n";
}
?>
// == is an operator which test
// 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 you can simply type
if ($show_separators) {
echo "<hr>\n";
}
?>
Converting to boolean
To explicitly convert a value to boolean, use either the (bool) or the (boolean) cast. However, in most cases you do not need to use the cast, 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
- an object with zero member variables
- the special type NULL (including unset variables)
Warning:
-1 is considered TRUE, like any other non-zero (whether
negative or positive) number!
<?php
echo gettype((bool) ""); // bool(false)
echo gettype((bool) 1); // bool(true)
echo gettype((bool) -2); // bool(true)
echo gettype((bool) "foo"); // bool(true)
echo gettype((bool) 2.3e5); // bool(true)
echo gettype((bool) array(12)); // bool(true)
echo gettype((bool) array()); // bool(false)
?>
echo gettype((bool) ""); // bool(false)
echo gettype((bool) 1); // bool(true)
echo gettype((bool) -2); // bool(true)
echo gettype((bool) "foo"); // bool(true)
echo gettype((bool) 2.3e5); // bool(true)
echo gettype((bool) array(12)); // bool(true)
echo gettype((bool) array()); // bool(false)
?>
