'' ) { return false; } /** * Deletes primary data and old data * * @abstract * * @param string $key Key. * @param string $group Group. * * @return boolean */ public function hard_delete( $key, $group = '' ) { return false; } /** * Flushes all data * * @abstract * * @param string $group Used to differentiate between groups of cache values. * * @return boolean */ public function flush( $group = '' ) { return false; } /** * Gets a key extension for "ahead generation" mode. * Used by AlwaysCached functionality to regenerate content * * @abstract * * @param string $group Used to differentiate between groups of cache values. * * @return array */ public function get_ahead_generation_extension( $group ) { return array(); } /** * Flushes group with before condition * * @abstract * * @param string $group Used to differentiate between groups of cache values. * @param array $extension Used to set a condition what version to flush. * * @return boolean */ public function flush_group_after_ahead_generation( $group, $extension ) { return false; } /** * Checks if engine can function properly in this environment * * @abstract * * @return bool */ public function available() { return true; } /** * Constructs key version key * * @abstract * * @param unknown $group Group. * * @return string */ protected function _get_key_version_key( $group = '' ) { return sprintf( 'w3tc_%d_%d_%s_%s_key_version', $this->_instance_id, $this->_blog_id, $this->_module, $group ); } /** * Constructs item key * * @abstract * * @param unknown $name Name. * * @return string */ public function get_item_key( $name ) { return sprintf( 'w3tc_%d_%s_%d_%s_%s', $this->_instance_id, $this->_host, $this->_blog_id, $this->_module, $name ); } /** * Use key as a counter and add integer value to it * * @abstract * * @param string $key Key. * @param int $value Value. * * @return bool */ public function counter_add( $key, $value ) { return false; } /** * Use key as a counter and add integer value to it * * @abstract * * @param string $key Key. * @param int $value Value. * * @return bool */ public function counter_set( $key, $value ) { return false; } /** * Get counter's value * * @abstract * * @param string $key Key. * * @return bool */ public function counter_get( $key ) { return false; } }