get_defined_constants()

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

返回所有常量的关联数组，键是常量名，值是常量值

说明

get_defined_constants([bool $categorize= false]): array

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

范例

Example #1get_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() 返回所有已定义函数的数组
• get_defined_vars() 返回由所有已定义变量所组成的数组

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

If you want to access directly on one category, just use:
<?php
print_r(get_defined_constants(true)['Core']);
?>
you can replace 'Core' by the category you wish (e.g. user):
<?php
print_r(get_defined_constants(true)['user']);
?>
Warning: only use this on development side

<?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;
}
?>

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] => 
)