(PECL apc >= 3.0.13)
apc_add — Cache a variable in the data store
Caches a variable in the data store, only if it's not already stored.
Note: Unlike many other mechanisms in PHP, variables stored using apc_add() will persist between requests (until the value is removed from the cache).
Store the variable using this name. key s are cache-unique, so attempting to use apc_add() to store data with a key that already exists will not overwrite the existing data, and will instead return FALSE. (This is the only difference between apc_add() and apc_store().)
The variable to store
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.).
如果成功则返回 TRUE，失败则返回 FALSE。
Example #1 A apc_add() example
<?php
$bar = 'BAR';
apc_add('foo', $bar);
var_dump(apc_fetch('foo'));
echo "\n";
$bar = 'NEVER GETS SET';
apc_add('foo', $bar);
var_dump(apc_fetch('foo'));
echo "\n";
?>
上例将输出：
string(3) "BAR" string(3) "BAR"