lchash is a little PHP extension that you can find at http://pecl.php.net/package/lchash which provides means of accessing and using native hash tables found in libC. The interface is really simple involving just 4 functions:

lchash_create() - initialize a new hash table lchash_destroy() - destroy a hash table lchash_insert() - insert key/value pair into the hash lchash_find() - retrieve a values based on key

By using this mechanism you can create a very fast and effecient memory-based data store for a script's duration.