/**
* Prepend data to an existing item.
*
* This method should throw an error if it is used with compressed data. This is an expected behavior.
* Memcached casts the value to be prepended to the initial value to the type of the initial value. Be
* careful as this leads to unexpected behavior at times. For instance, prepending (float) 45.23 to
* (int) 23 will result in 45, because the value is first combined (45.2323) then cast to "integer"
* (the original value), which will be (int) 45. Due to how memcached treats types, the behavior has been
* mimicked in the internal cache to produce similar results and improve consistency. It is recommend
* that prepends only occur with data of the same type.
*
* @link http://www.php.net/manual/en/memcached.prepend.php
*
* @param string $key The key under which to store the value.
* @param string $value Must be string as prepending mixed values is not well-defined.
* @param string $group The group value prepended to the $key.
* @param string $server_key The key identifying the server to store the value on.
* @param bool $byKey True to store in internal cache by key; false to not store by key
* @return bool Returns TRUE on success or FALSE on failure.
*/
public function prepend($key, $value, $group = 'default', $server_key = '', $byKey = false)
{
if (!is_string($value) && !is_int($value) && !is_float($value)) {
return false;
}
$derived_key = $this->buildKey($key, $group);
// If group is a non-Memcached group, prepend to runtime cache value, not Memcached
if (in_array($group, $this->no_mc_groups)) {
if (!isset($this->cache[$derived_key])) {
return false;
}
$combined = $this->combine_values($this->cache[$derived_key], $value, 'pre');
$this->add_to_internal_cache($derived_key, $combined);
return true;
}
// Append to Memcached value
if (false !== $byKey) {
$result = $this->mc->prependByKey($server_key, $derived_key, $value);
} else {
$result = $this->mc->prepend($derived_key, $value);
}
// Store in runtime cache if add was successful
if (Memcached::RES_SUCCESS === $this->getResultCode()) {
$combined = $this->combine_values($this->cache[$derived_key], $value, 'pre');
$this->add_to_internal_cache($derived_key, $combined);
}
return $result;
}
/**
* @inheritdoc
*/
public function prependByKey($server_key, $key, $value, $expiration = null)
{
$key = $this->prefix . $key;
return parent::prependByKey($server_key, $key, $value, $expiration);
}
