PHP: Booleans Syntax

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.

copy to clipboard

<?php
$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.

copy to clipboard

<?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";
}
?>

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)

Every other value is considered TRUE (including any resource).

Warning:

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

copy to clipboard

<?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)
?>