apc_define_constants()

(PECL apc >= 3.0.0)

Defines a set of constants for retrieval and mass-definition

说明

apc_define_constants(string $key,array $constants[,bool $case_sensitive= TRUE]): bool

define() is notoriously slow. Since the main benefit of APC is to increase the performance of scripts/applications, this mechanism is provided to streamline the process of mass constant definition. However, this function does not perform as well as anticipated.

For a better-performing solution, try the » hidef extension from PECL.

Note: To remove a set of stored constants(without clearing the entire cache), an empty array may be passed as the$constantsparameter, effectively clearing the stored value(s).

参数

$key: The$keyserves as the name of the constant set being stored. This$keyis used to retrieve the stored constants in apc_load_constants().
$constants: An associative array ofconstant_name => valuepairs. Theconstant_namemust follow the normal constant naming rules.valuemust evaluate to a scalar value.
$case_sensitive: The default behaviour for constants is to be declared case-sensitive; i.e.CONSTANTandConstantrepresent different values. If this parameter evaluates to FALSE the constants will be declared as case-insensitive symbols.

返回值

成功时返回TRUE，或者在失败时返回FALSE。

范例

Example #1 apc_define_constants() example

<?php
$constants = array(
    'ONE'   => 1,
    'TWO'   => 2,
    'THREE' => 3,
);
apc_define_constants('numbers', $constants);
echo ONE, TWO, THREE;
?>

以上例程会输出：

参见

apc_load_constants()Loads a set of constants from the cache
define()定义一个常量
constant()返回一个常量的值
Or the PHP constants reference

It doesn't introduce much overhead if you make use of conditional function definitions:
<?php
if (function_exists('apc_load_constants')) {
  function define_array($key, $arr, $case_sensitive = true)
  {
    if (!apc_load_constants($key, $case_sensitive)) {
      apc_define_constants($key, $arr, $case_sensitive);
    }
  }
} else {
  function define_array($key, $arr, $case_sensitive = true)
  {
    foreach ($arr as $name => $value)
      define($name, $value, $case_sensitive);
  }
}
//in your code you just write something like this:
define_array('NUMBERS', Array('ONE' => 1, 'TWO' => 2, 'THREE' => 3));
?>

An observation that I've made is that the nature of apc_define_constants() binding the list of constants to a key and then requiring that key to load the constants is limiting. Furthermore, there's no way to append additional constants to a given key.
A solution that I've been adopting is to build a list of constants to be defined, and then do one of two things:
1) if APC is enabled, then use apc_define_constants();
2) ...else loop through the list and define each constant normally.
The problem I've run into is when this process happens at different places in a large application, it can introduce overhead that otherwise wouldn't be there if it was possible to append to an existing list of defined constants in APC.