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defineDefiniert eine benannte Konstante


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

Definiert während der Laufzeit eine benannte Konstante.



Der Name der Konstante


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.


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.


Groß-/Kleinschreibungsunabhängige Konstanten werden kleingeschrieben gespeichert.


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


Beispiel #1 Konstanten definieren

("KONSTANTE""Hallo Welt.");
KONSTANTE// gibt "Hallo Welt." aus
echo Konstante// gibt "Konstante" aus und erzeugt eine Benachrichtigung

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


Siehe auch

30 BenutzerBeiträge:
- Beiträge aktualisieren...
angelos at unkreativ dot org
9.01.2011 10:18
Something I found out the "hard" way today: integers starting with 0 won't work.
('SOMECONSTANT', 09900);
Produces int(0)

Produces int(9900)
toph at farmer corp dot c om
16.10.2010 11:51

Here is a trick to use constants within the heredoc notation.

('MY_CONSTANT','foo bar')
$cst = 'cst';

$string = <<<EOF
My constante MY_CONSTANT : {$cst(MY_CONSTANT)} ...

That will echo :

My constante MY_CONSTANT : foo bar ...

As you can use function within the heredoc notation the idea is to use a fonction to return the value of the constant.
Be carefull, to use a function, it's necessary to declare the name of the function as a variable and to use that varaible during the "call" of the constant.

It works for me and doesn't seem too messy.

Hope that will help.
rush at bigup dot com dot pa
10.08.2010 19:23
Just in case:

You cannot set a constant to be a class.  For example:
define ("WSDLCLIENT",new soapclient(WSDLSERVER, 'wsdl'));

You cannot do this.
chris at peeto dot net
26.03.2010 4:15
The value of a constant can be the value of another constant.


("NEW_GOOD_NAME_CONSTANT", "I have a value");

echo OLD_BAD_NAME_CONSTANT; // legacy

16.08.2009 2:54
Note that define don't care at all about the constant name, you can give everything as a constant name, even if the PHP documentation says that the allowed characters are [a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*

Just try this :

<?php define('anything::()$', 'test'); ?>

You won't be able to access this constant though, it will throw a parse error, either through constant() or define(), but if you do that :

<?php print_r(get_defined_constants()); ?>

You will see that the constant is registered at the end of the array. Yes that's totally useless. But you can try other things that will work with constant() :

<?php define('...', 'test'); echo constant('...'); ?>

Will echo 'test'. Yeah that's a pretty strange behavior.

And please note that defining object constants outside of objets don't work :

class myObject { }
define('myObject::CONSTANT', 'test');
20.07.2009 7:31
My notice to: redeclare define -  it is possible

php -v

--> PHP 5.2.6-3ubuntu4.1 with Suhosin-Patch
Zend Engine v2.2.0, Copyright (c) 1998-2008 Zend Technologies
php -r "define('TEST','foo',true);

string(3) "foo"
string(3) "bar"

sixd at php dot net
17.07.2009 23:24
A note on redefining:

Constants can't be redefined:

$ php -r "define('A', 1); var_dump('A'); define('A', 2); var_dump('A');";
string(1) "A"
PHP Notice:  Constant A already defined in Command line code on line 1
string(1) "A"

But using the case insensitive setting shows that the internal
representation is lower case:

$ php -r "define('A', 1, true); var_dump('A'); define('A', 2); var_dump('A');";
string(1) "A"
string(1) "A"

Note the lower case 'a' in the second define() here:
$ php -r "define('A', 1, true); var_dump('A'); define('a', 2); var_dump('A');";
string(1) "A"
PHP Notice:  Constant a already defined in Command line code on line 1
string(1) "A"
danbettles at yahoo dot co dot uk
14.04.2009 20:56
define() will define constants exactly as specified.  So, if you want to define a constant in a namespace, you will need to specify the namespace in your call to define(), even if you're calling define() from within a namespace.  The following examples will make it clear.

The following code will define the constant "MESSAGE" in the global namespace (i.e. "\MESSAGE").

namespace test;
define('MESSAGE', 'Hello world!');

The following code will define two constants in the "test" namespace.

namespace test;
define('test\HELLO', 'Hello world!');
define(__NAMESPACE__ . '\GOODBYE', 'Goodbye cruel world!');
27.03.2009 17:24
This code will define every key of an array, and if its a multidimentional array it will define it as parent_child1_child2_etc.

function define_array( $array, $keys = NULL )
$array as $key => $value )
$keyname = ($keys ? $keys . "_" : "") . $key;
is_array( $array[$key] ) )
define_array( $array[$key], $keyname );
define( $keyname, $value );
ceo at l-i-e dot com
11.03.2009 23:04
In PHP 4.4.9, you cannot use certain names for constants.

Specifically, reserved words such as 'PRINT', 'IF', etc.

Oddly enough, you get different behaviour for some:

('IF', 42);
"IF: ", IF, "<hr />\n";

yields PHP Parse error:  syntax error, unexpected T_IF

('PRINT', 13);
"PRINT: ", PRINT, "<hr />\n";

yields PHP Parse error:  syntax error, unexpected ')'

Not sure if this is still true in PHP 5 or not, but it's worth noting if it is.
9.03.2009 22:03
With php 5.30 it is possible to make some "restrictions", in case u use namespaces...
The following function allows only uppercase and, if 3 param isset, gives E_USER_ERROR instead of E_NOTICE:

namespace bla;

define($c,$v,$x=false) {
$c = strtoupper($c);
    if (!
defined($c)) {
// not to use \define here, as the syntax highlighting does not work correctly here...
return define($c, $v, true);
    } else if (
$x == true) {
trigger_error('setting constant "'.$c.'" is not allowed', E_USER_ERROR);

define('PHP_VERSION', '1');
define('PHP_VERSION', '1') || trigger_error('constant already defined', E_USER_NOTICE);
define('PHP_VERSION', '1', true);
jv at vip dot ie
9.03.2009 1:14
Probably the most efficient way of creating a constant array is to put it in a function like this:

function my_const_arr()
   return array
'key1' => 'val 1',
'key2' => 'va' 2'

Then use at will like so...
<?php $my_const_arr = my_const_arr(); ?>
usuroer dot king at hotmail dot co dot uk
8.03.2009 13:15
Referring to "This-Is-A-Test" constant below.

When echoing it the script thinks you performing a series of minus (subtraction) thus since THIS and IS, A, TEST are not defined they are 0 by default. So 0-0-0-0 = 0.

As explained that a hyphen cannot be used within a variable.
downwind at web dot de
2.02.2009 5:48
I'm reffering to the note below by mittiprovence.

The described behavior has nothing to do with the fact that there is a constant in the condition.

Comparing a non-numeric string to the integer 0 by using == will return true, since the string will be casted to integer - which will be zero. If your string starts with a number, it will be castet to an integer with the number as value.

To avoid the described behavior, you should use === instead of ==.

Finally, the behavior discribed by mittiprovence is exacly the expected behavior as defined in the manual.

For further information read the manual: #language.types.string.conversion


if (0 == "some string") { // is true
echo "0 == 'some string'";

if (
1 == "some string") { // is false
echo "1 == 'some string'";

if (
1 == "1 some string") { // is true
echo "1 == '1 some string'";

if (
0 === "some string") { // is false
echo "0 === 'some string'";

eparkerii at carolina dot rr dot com
22.10.2008 21:01
Found something interesting.  The following define:

("THIS-IS-A-TEST","This is a test");

Will return a '0'.

Whereas this:

("THIS_IS_A_TEST","This is a test");

Will return 'This is a test'.

This may be common knowledge but I only found out a few minutes ago.

[EDIT BY danbrown AT php DOT net: The original poster is referring to the hyphens versus underscores.  Hyphens do not work in defines or variables, which is expected behavior.]
2.09.2008 1:41
A better solution to that of thscheer at web dot de, is to simply serialize the array.

for example:


= array("apple", "banana", "orange");

define("FRUITS", serialize($fruits));

// Now to use it
$my_fruits = unserialize(FRUITS);


As you can see this is a much simpler and more efficient way to stuff arrays into constants.
jan at webfontein dot nl
27.07.2008 14:20
For translating with variables and define, take also a look on the constant() function.

Example :

('PAYMENT_IDEAL',"iDEAL Payment ( NL only )");
define('PAYMENT_MASTERCARD',"Mastercard Payment ( international )");



// output :
// Mastercard Payment ( international )
thscheer at web dot de
20.06.2008 11:18
How to define an array as constant with define?

there is a simple way to define an array of values as constant...


define ("constant-name","value1,value2,value3,value4");

$t_array = preg_split('/,/', constant(constant-name), -1, PREG_SPLIT_NO_EMPTY);


array(4) { [0]=> string(6) "value1" [1]=> string(6) "value2" [2]=> string(6) "value3" [3]=> string(6) "value4" }

Now you can iterate over the array defined as constant ...
ceo at l-i-e dot com
5.05.2008 17:30
I'm not sure if it's version dependent, but apparently this works:
define('APPLICATION_NOW', time());

This can be quite handy for time-dependent code...

You can then do:
class foo {
  $private now = APPLICATION_NOW;

and have a consistent time-stamp across the application, which is nice.

Works for me in 5.2.5

I didn't think it worked before...
jason@sitehatchery dot com
25.04.2008 8:28
You can store your constant as the value of a variable like this:


To access the constant, do this:  constant($variable).

Beware: if your variable changes, then you loose your reference to the constant - but the constant itself will not change.

I've found this especially useful for storing the constant string   (i.e. VARIABLE) in a database.
rayro at gmx dot de
15.09.2007 23:53
just a note to the previous post by e s lin d sey at g mail dot co m:

Well as u said, it is not the best workaround. To resolve this "Problem" without getting incredible loss of performance, you are able to make the use of "variable functions" like "variable variables":

= 'constant';
$string = <<<END
    This is PHP running on<br />

In this example we make use of the "constant" function which is builtin, and it will output:

string(37) " This is PHP running on

Tested on PHP 5...
Best regards
e s lin d sey at g mail dot co m
13.08.2007 22:38
Constants can't be referenced from within quotes or (more importantly IMHO) from within HEREDOC syntax. This is a huge drawback in my opinion. Here's two of my workarounds:


//PHP5 only -- more efficient
$constarray = get_defined_constants(true);
$constarray['user'] as $key => $val)
sprintf('$_CONSTANTS[\'%s\'] = \'%s\';', addslashes($key), addslashes($val)));

//PHP4+ -- less efficient because it defines (potentially) hundreds of unnecessary constants
foreach(get_defined_constants() as $key => $val)
sprintf('$_CONSTANTS[\'%s\'] = \'%s\';', addslashes($key), addslashes($val)));


Now you can refer to your defined constants using the $_CONSTANTS array. Note that because this is NOT a superglobal, a few caveats apply:


//run code snippet here to define $_CONSTANTS in global scope...

$mv = $_CONSTANTS['FOO']; //works

function my_function1()
$mv = $_CONSTANTS['BAR']; //doesn't work! not defined!

$mv = $_CONSTANTS['BAR']; //ah, this works!


I realize this is not ideal, either for performance or for convenience of being able to refer to constants without regard to scope, but it is a workaround that works. Depending on your application, it may be easier to shift your paradigm a bit and use the following method instead, declaring your constants as variables first:


//first, define our constants...
$_CONSTANTS['FOO'] = 'bar';
$_CONSTANTS['BAR'] = 'foo';

//now, turn them into real constants...
foreach($_CONSTANTS as $key => $val)
define($key, $val);

//now, you can use either format to refer to a constant
print($_CONSTANTS['FOO']);   //prints 'bar'
print(FOO);                  //prints 'bar'
print("$_CONSTANTS['FOO']"); //prints 'bar'
                             //prints 'blah bar blah'
print <<<EOF
  blah {$_CONSTANTS['FOO']} blah


Hope this helps some of you out there, I know being able to utilize my constants in HEREDOC helped me a ton!
smifffy at smith-net dot org dot uk
26.07.2007 1:23
a basic function to auto assign a numeric value that increase by itself each time - used in some permission style scripts

function define_bitwise($constant_name, $reset = False)
$bitwise_next = 1;

    if (
$reset === True )
$bitwise_next = 1;

define($constant_name, $bitwise_next);
$bitwise_next += $bitwise_next;

when reset it set to True, resets that value to 1 and starts afresh
creeves at dja dot com
19.07.2007 15:59
Intersting to note:

I found this in php5 on windows

If you try to unset a constant (which you cant but maybe you have a Jr. programmer or something).  The error message that is thrown is:

("SOME_CONSTANT", true);
unset (

Parse error: parse error, unexpected ')', expecting T_PAAMAYIM_NEKUDOTAYIM
nl-x at bita dot nl
9.07.2007 19:34
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.
stangelanda at arrowquick dot com
1.01.2007 3:59
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:
function adefine($constant_name, $value=null) {
$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.
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

12.02.2005 5:45
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.

= array(

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

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




phpnet at trenkner dot de
15.03.2003 0:59
---[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
7.11.2001 5:45
Wonder how to work with variable which name is stored in a constant?
Here it is:
// assigning value
${VAR_NAME} = "value";
// getting value back
echo ${VAR_NAME};
ste at opk dot no
29.08.2001 19:41
To use a constant to show an element of an array inside a string:
define ('C', 0); print ("element 0: {$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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