get_defined_constants

(PHP 4 >= 4.1.0, PHP 5, PHP 7)

get_defined_constants — 返回所有常量的关联数组，键是常量名，值是常量值

说明

array get_defined_constants ([ bool $categorize = false ] )

返回当前所有已定义的常量名和值。这包含 define() 函数所创建的，也包含了所有扩展所创建的。

参数

categorize

让此函数返回一个多维数组，分类为第一维的键名，常量和它们的值位于第二维。

  <?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

返回的数组为常量名 => 常量值，也可以按注册变量的扩展名称来分组。

更新日志

版本	说明
5.3.1	仅作用于 Windows：内核常量归类到 Core，之前是 mhash。
5.3.0	内核常量归类为 Core，之前是 internal。在 Windows 上，内核常量归类到 mhash。
5.2.11	`categorize` 参数现在可以合适得被处理。在此之前，`categorize` 被解释为 !is_null($categorize)，导致任何非 `NULL` 的值会强制常量分类。
5.0.0	增加了参数 `categorize`。

范例

Example #1 get_defined_constants() 例子

  <?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

defined() - 检查某个名称的常量是否存在
get_loaded_extensions() - 返回所有编译并加载模块名的 array
get_defined_functions() - Returns an array of all defined functions
get_defined_vars() - 返回由所有已定义变量所组成的数组

用户评论:

[#1] bimal at sanjaal dot com [2013-02-28 09:10:33]

Though the syntax editors mark the following as error, it executes successfully under PHP, as you desire.

<?php $user_defined_constants=get_defined_constants(true)['user']; print_r($user_defined_constants); ?>

No errors/warnings seen.
Only the special thing here is, you are passing true to the function, and extracting the result's 'user' index directly.

[#2] Bob [2008-08-07 21:50:34]

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

[#3] [2006-01-05 11:29:09]

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] =>
)

[#4] me at gogogadgetscott dot info [2005-06-18 11:14:22]

<?php function sch_get_consant($value) { $constants = get_defined_constants(); $name = array_search($value, $constants, TRUE); return $name; } ?>