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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

说明

array get_defined_constants ([ bool $categorize = false ] )

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.

参数

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));
?>

以上例程的输出类似于：

Array
(
    [Core] => 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
        )

)

返回值

更新日志

版本 说明
5.3.1 Windows only: Core constants are categorized under Core, previously mhash.
5.3.0 Core constants are categorized under Core, previously internal. On Windows, the Core Constants are categorized under mhash.
5.2.11 The categorize parameter now operates appropriately. Previously, the categorize parameter was interpreted as !is_null($categorize), making any value other than NULL force the constants to be categorized.
5.0.0 The categorize parameter was added.

范例

Example #1 get_defined_constants() Example

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

以上例程的输出类似于：

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
)

参见

PHP 选项/信息 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: Returns an associative array with the names of all the constants and their values

用户评论:

Bob (08-Aug-2008 05:50)

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 (13-Aug-2007 09:12)

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
}

?>

(05-Jan-2006 07:29)

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 (18-Jun-2005 07:14)

<?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;
}
?>