memcached-php-callbacks-php-read-through-6

  • Callbacks

    • Read-through cache callbacks

  • Read-through cache callbacks

    • Read-through cache callbacks

    Read-through cache callbacks

    Read-through cache callbacks are invoked when an
    item cannot be retrieved from the server. The callback is passed
    the Memcached object, the requested key, and the by-reference value
    variable. The callback is responsible for setting the value and
    returning true or false. If the callback returns true, Memcached
    will store the populated value on the server and return it to the
    original calling function. Only Memcached::get()
    and Memcached::getByKey() support these
    callbacks, because the memcache protocol does not provide
    information on which keys were not found in the multi-key
    request.

    Example #1 Read-through callback example

    <?php
    $m     = new Memcached();
    $m->addServer('localhost', 11211);

    $profile_info = $m->get('user:'.$user_id, 'user_info_cb');

    function user_info_cb($memc, $key, &$value)
    {
            $user_id = substr($key, 5);
            /* lookup profile info in the DB */
        /* ... */
            $value = $profile_info;
        return     true;
    }
    ?>