Booleans

Booleans

The type only has two values, and is used to express a truth value. It can be either true or false. bool

Syntax

To specify a literal, use the constants true or false. Both are case-insensitive. bool

<?php
$foo = True; // assign the value TRUE to $foo
?>

Typically, the result of an which returns a value is passed on to a . operatorboolcontrol structure

<?php
$action = "show_version";
$show_separators = true;

// == 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 , use the 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 . For more information see the page. bool``(bool)``boolType Juggling

When converting to , the following values are considered false: bool

• the false itself boolean

• the (zero) integer0

• the s and (zero) float0.0``-0.0

• the empty , and the string""string"0"

• an with zero elements array

• the unit type (including unset variables) NULL

• Internal objects that overload their casting behaviour to bool. For example: objects created from empty elements without attributes. SimpleXML

  Every other value is considered true (including and ). resourceNAN

Waarschuwing: > is considered true, like any other non-zero (whether negative or positive) number! -1

Voorbeeld: Casting to Boolean

<?php
var_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)
?>