# apcu_entry

(PECL apcu >= 5.1.0)

apcu_entry — Atomically fetch or generate a cache entry

### 说明

apcu_entry ( string `$key` , callable `$generator` [, int `$ttl` = 0 ] ) : mixed

Atomically attempts to find `key` in the cache, if it cannot be found `generator` is called, passing `key` as the only argument. The return value of the call is then cached with the optionally specified `ttl`, and returned.

> Note: When control enters apcu_entry() the lock for the cache is acquired exclusively, it is released when control leaves apcu_entry(): In effect, this turns the body of `generator` into a critical section, disallowing two processes from executing the same code paths concurrently. In addition, it prohibits the concurrent execution of any other APCu functions, since they will acquire the same lock.

Warning

The only APCu function that can be called safely by `generator` is apcu_entry().

### 参数

`key`

  Identity of cache entry

`generator`

  A callable that accepts `key` as the only argument and returns the value to cache.

`ttl`

  Time To Live; store `var` in the cache for `ttl` seconds. After the `ttl` has passed, the stored variable will be expunged from the cache (on the next request). If no `ttl` is supplied (or if the `ttl` is 0), the value will persist until it is removed from the cache manually, or otherwise fails to exist in the cache (clear, restart, etc.).

### 返回值

Returns the cached value

### 范例

Example #1 An apcu_entry() example

    <?php
    $config = apcu_entry("config", function($key) {
     return [
       "fruit" => apcu_entry("config.fruit", function($key){
         return [
           "apples",
           "pears"
         ];
       }),
       "people" => apcu_entry("config.people", function($key){
         return [
          "bob",
          "joe",
          "niki"
         ];
       })
     ];
    });

    var_dump($config);
    ?>

以上例程会输出：

    array(2) {
      ["fruit"]=>
      array(2) {
        [0]=>
        string(6) "apples"
        [1]=>
        string(5) "pears"
      }
      ["people"]=>
      array(3) {
        [0]=>
        string(3) "bob"
        [1]=>
        string(3) "joe"
        [2]=>
        string(4) "niki"
      }
    }

### 参见

- apcu_store() - Cache a variable in the data store
- apcu_fetch() - Fetch a stored variable from the cache
- apcu_delete() - Removes a stored variable from the cache