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defined> <constant
Last updated: Fri, 18 May 2012

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define

(PHP 4, PHP 5)

define — Definiert eine benannte Konstante

Beschreibung

bool define ( string $name , mixed $value [, bool $case_insensitive = false ] )

Definiert während der Laufzeit eine benannte Konstante.

Parameter-Liste

name

Der Name der Konstante

value

Der Wert der Konstante. Es sind nur Skalar- und NULL-Werte erlaubt. Skalarwerte sind Ganzzahlen, Gleitkommazahlen, Zeichenketten oder boolsche Werte. Es ist möglich, Konstanten vom Typ Ressource zu definieren, allerdings wird dies nicht empfohlen, da es unvorhersagbares Verhalten des Programms zur Folge haben kann.

case_insensitive

Falls auf TRUE gesetzt, wird bei der Konstante nicht zwischen Groß- und Kleinschreibung unterschieden. In der Voreinstellung wird zwischen Groß- und Kleinschreibung unterschieden, d.h KONSTANTE und Konstante repräsentieren unterschiedliche Werte.

Hinweis:

Groß-/Kleinschreibungsunabhängige Konstanten werden kleingeschrieben gespeichert.

Rückgabewerte

Gibt bei Erfolg TRUE zurück. Im Fehlerfall wird FALSE zurückgegeben.

Beispiele

Beispiel #1 Konstanten definieren

<?php
define("KONSTANTE", "Hallo Welt.");
echo KONSTANTE; // gibt "Hallo Welt." aus
echo Konstante; // gibt "Konstante" aus und erzeugt eine Benachrichtigung

define("BEGRUESSUNG", "Hallo Du.", true);
echo BEGRUESSUNG; // gibt "Hallo Du." aus
echo Begruessung; // gibt "Hallo Du." aus

?>

Siehe auch



add a note add a note User Contributed Notes
define
nl-x at bita dot nl
09-Jul-2007 07:34
Watch out. You can define a new constant with the name NULL with define("NULL","FOO");. But you must use the function constant("NULL"); to get it's value. NULL without the function call to the constant() function will still retrieve the special type NULL value.
Within a class there is no problem, as const NULL="Foo"; will be accessible as myClass::NULL.
dont care
03-Jun-2007 11:19
chris at frecod dot de, you might just use SQL for this:
NOT IN(var1,var2,var3,var4,var5,var6)
stangelanda at arrowquick dot com
01-Jan-2007 03:59
An improvement on the function from bobbykjack at yahoo dot co dot uk on the concept by richard dot quadling at bandvulc dot co dot uk:
<?php
function adefine($constant_name, $value=null) {
    static $increment = 0; // 1 for bitmask

    if (is_null($value)) {
        define($constant_name, ++$increment); // $increment=$increment<<1 for bitmask
    } else {
        define($constant_name, $value);
        if (is_numeric($value)) {
            $increment = $value;
        }
    }
}
?>
If you pass it a second argument it defines it normally, and resets the increment if the value is numeric.  This way the function can replace define, and you can reset the counter for a new set of constants.
<?php
adefine ('RULE_CALLBACK_FORMAT', 1); // 1
adefine ('RULE_CHANGE_CALLBACK_ON_ERROR'); // 2
adefine ('RULE_CHANGE_COMPARE_DATE'); // 3
adefine('KEYWORD', 'hodgepodge'); // hodgepodge <-- defined normally
adefine ('RULE_CHANGE_ON_DATE'); // 4

adefine ('ERROR_DESC', 1); // 1 <-- Counter reset
adefine ('ERROR_EXPECTED_RESULT'); // 2
?>
IK
15-Nov-2005 03:42
[Editor's Note: Obviously, constants cannot be redefined. That is the meaning of a constant.]

Just a quick note.. If a constant is once defined, any subsequent attempts to define it once again are ignored.

<?
define('WHAT_DID_YOU_EXPECT', 'First');
define('WHAT_DID_YOU_EXPECT', 'Second');
echo WHAT_DID_YOU_EXPECT
?>

Outputs 'First'.

I really thought I have gone mad when I saw just the last two lines of code (the first one was in another file) and it was echoing 'First'..
12-Feb-2005 05:45
Better pack with define() for all who really miss Java package management:

Use this "manifest.php" on very first script start or copy it to your config.somehow.php.

<?php
$__packages = array(
    "org.ilove.java.more",
    "org.ilove.python.too",
    "net.php.isok"
);

define("C_IS_WINDOWS", false);
define("C_DIR", (C_IS_WINDOWS ? "\\" : "/"));
define("C_PATH_ROOT", str_replace("/", C_DIR, $_SERVER["DOCUMENT_ROOT"]).C_DIR);
define("C_PATH_CORE", C_PATH_ROOT."core".C_DIR);
define("C_PATH_CLASS", C_PATH_CORE."classes".C_DIR);
define("C_APPLICATION_BASE", C_PATH_CORE.C_DIR."application".C_DIR);

$total_packages = 0;
$i = sizeof($__packages);
while($i-- > 0) {
    $tokens = explode(".", $__packages[$i]);
    $j = sizeof($tokens);
    while($j-- > 0) {
        $token = strtolower(trim($tokens[$j]));
        if(strlen($token) > 0 && !defined($token)) {
            define($token, ($j == 0 ? C_PATH_CLASS : "").$tokens[$j].C_DIR);
            $total_packages++;
        }
    }
}
define("C_PACKAGE_COUNT", $total_packages);
?>

With restrictions on non-package constants, you now can call your files like that:

<?php

require_once org.ilove.java.more."Than.php";

?>

Regards
Robi
phpnet at trenkner dot de
15-Mar-2003 12:59
---[Editor's Note]---
As of PHP 5.0.0 this is possible. You can define class-only constants, which can be called like Foo::Constant1 from the outside
---[End Note]---

Please keep in mind that

class AClass {
  define ("Const1", "Value1");
  ... }

didn't work. You have to make all your constant definitions before you open the class. So

define ("Const1", "Value1");
class AClass {
  ... }

would be correct.
radovan dot biciste at managestar dot com
07-Nov-2001 05:45
Wonder how to work with variable which name is stored in a constant?
Here it is:
<?php
define("VAR_NAME","test");
// assigning value
${VAR_NAME} = "value";
// getting value back
echo ${VAR_NAME};
?>
ste at opk dot no
29-Aug-2001 07:41
To use a constant to show an element of an array inside a string:
define ('C', 0); print ("element 0: {$a[C]}");
The { & } around the variable signals that what's inside should be treated as a variable and not a string.
Note that 'print ("a constant:{C}");' wont work as ZERO is a constant.
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defined> <constant
Last updated: Fri, 18 May 2012