Last updated: Fri, 20 Nov 2009

get_defined_constants

(PHP 4 >= 4.1.0, PHP 5)

get_defined_constants — Returns an associative array with the names of all the constants and their values

Description

array get_defined_constants ([ bool $categorize ] )

Returns the names and values of all the constants currently defined. This includes those created by extensions as well as those created with the define() function.

Parameters

categorize

Causing this function to return a multi-dimensional array with categories in the keys of the first dimension and constants and their values in the second dimension.


<?php
define("MY_CONSTANT", 1);
print_r(get_defined_constants(true));
?>

The above example will output something similar to:

Array
(
    [internal] => Array
        (
            [E_ERROR] => 1
            [E_WARNING] => 2
            [E_PARSE] => 4
            [E_NOTICE] => 8
            [E_CORE_ERROR] => 16
            [E_CORE_WARNING] => 32
            [E_COMPILE_ERROR] => 64
            [E_COMPILE_WARNING] => 128
            [E_USER_ERROR] => 256
            [E_USER_WARNING] => 512
            [E_USER_NOTICE] => 1024
            [E_ALL] => 2047
            [TRUE] => 1
        )

    [pcre] => Array
        (
            [PREG_PATTERN_ORDER] => 1
            [PREG_SET_ORDER] => 2
            [PREG_OFFSET_CAPTURE] => 256
            [PREG_SPLIT_NO_EMPTY] => 1
            [PREG_SPLIT_DELIM_CAPTURE] => 2
            [PREG_SPLIT_OFFSET_CAPTURE] => 4
            [PREG_GREP_INVERT] => 1
        )

    [user] => Array
        (
            [MY_CONSTANT] => 1
        )

)

Return Values

Changelog

Version	Description
5.0.0	The `categorize` parameter was added.

Examples

Example #1 get_defined_constants() Example


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

The above example will output something similar to:

Array
(
    [E_ERROR] => 1
    [E_WARNING] => 2
    [E_PARSE] => 4
    [E_NOTICE] => 8
    [E_CORE_ERROR] => 16
    [E_CORE_WARNING] => 32
    [E_COMPILE_ERROR] => 64
    [E_COMPILE_WARNING] => 128
    [E_USER_ERROR] => 256
    [E_USER_WARNING] => 512
    [E_USER_NOTICE] => 1024
    [E_ALL] => 2047
    [TRUE] => 1
)


Add this method to your class definition if you want an array of class constants (get_defined_constants doesn't work with class constants as Peter P said above):



<?php

public function get_class_constants()

{

    $reflect = new ReflectionClass(get_class($this));

    return $reflect->getConstants());

}

?>



You could also override stdObject with it so that all your classes  have this method

eslindsey AT gma il dot co m
14-Aug-2007 05:12


If you need to use the values of your defined constants in strings or for example in HEREDOC syntax, use this function:



<?php



//PHP5+ only

$constarray = get_defined_constants(true);

foreach($constarray['user'] as $key => $val)

    eval(sprintf('$_CONSTANTS[\'%s\'] = \'%s\';', addslashes($key), addslashes($val)));



//PHP4+ ...this is less efficient since it defines hundreds of constants

foreach(get_defined_constants() as $key => $val)

    eval(sprintf('$_CONSTANTS[\'%s\'] = \'%s\';', addslashes($key), addslashes($val)));



?>



Once you run that you can use $_CONSTANTS['constantname'] to get the value of a constant. You'll need to erase the array and rerun the code if you define any new constants. But I found it handy when I wanted to use a couple of my defined constants in HEREDOC syntax. Don't forget: because this is not really a superglobal you'll need to globalize it if you want to use it from within a different scope, for example:



<?php



//hopefully you ran the snippet out here so that $_CONSTANTS is in global scope.



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



function my_function()

{

    global $_CONSTANTS;       //without this line it won't work in here!

    $mv = $_CONSTANTS['bar']; //works thanks to previous line

}



?>

Peter P.
07-Jul-2007 09:38


Does not return class constants in PHP 5.

06-Jan-2006 04:29


If you want to filter through and return only the prefix for your constants (i.e. you have constants with a naming scheme), then you can use this quick little function. It comes in handy for debugging.



<?php

function returnConstants ($prefix) {

    foreach (get_defined_constants() as $key=>$value) 

        if (substr($key,0,strlen($prefix))==$prefix)  $dump[$key] = $value; 

    if(empty($dump)) { return "Error: No Constants found with prefix '".$prefix."'"; }

    else { return $dump; }

}

?>



Example:



<?php

define("SITENAME_OPTION_ONE",true);

define("SITENAME_OPTION_TWO",false);

define("SITENAME_URL","foo");



print_r(returnConstants("SITENAME_OPTION"));

?>



Will return:



Array

(

    [SITENAME_OPTIONONE] => 1

    [SITENAME_OPTIONTWO] => 

)

me at gogogadgetscott dot info
19-Jun-2005 03:14


<?php

/**

 * Convert constant value into string name.

 *

 * @param  mixed  Constant value.

 * @return string Constant name.

 * @access public

 */

function sch_get_consant($value)

{

    $constants = get_defined_constants();

    $name = array_search($value, $constants, TRUE);    

    return $name;

}

?>

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