php Prepare statement

<?PHP
/**
 * Prepare statement loading from Config
 * The ctime on dabase instance config could be used to control the expire * of all prepared statments
 * Config ctime = now() could be used to force recompile for each bootstrap, 
 * date +%s could get the value of current seconds from EPOCH
 * stmts will be name => query pairs 
 * Expired will be recompile automatically, any update on config should update ctime as well
 *
 * @author Anthony.chen 
 * 2010-2012 reserved
 */
class PSTMT{

    public static $instances = array();

    /**
     * Loading the prepare statment from DB Connection
     * The stmts is config linked to DB instance with 'stmts' k=>v array
     *
     * @return Boolean
     */
    public static function prepare($db='default'){
        //Getting statment from config
        $_config = Pexcel::config('database')->$db;
        $_ctime = Arr::get($_config,'ctime',0);
        $_configStmts = Arr::get($_config,'stmts',NULL);
        if($_configStmts != NULL){//There is statments configured
            if(!isset(self::$instances[$db])){
                $_sql = 'select name , EXTRACT(EPOCH FROM prepare_time) as ctime from pg_prepared_statements';
                $_pstmts = DB::query(DB::SELECT,$_sql,true)->execute($db)->as_array();
                if(!$_pstmts){
                    self::$instances[$db] = array();
                }else{
                    //Log::debug('Before Commpiling,statement Found');
                    foreach($_pstmts as $_pstmt){
                        self::$instances[$db][$_pstmt->name] = $_pstmt->ctime;
                    }
                }
            }
            //Compile the statments
            foreach($_configStmts as $stmtName => $stmtQuery){
                if(isset(self::$instances[$db][$stmtName])){
                    if( self::$instances[$db][$stmtName] < $_ctime){
                        //Log::debug($stmtName.' Expires');
                    }else{
                        //Log::debug($stmtName.' Exists');
                        continue;
                    }
                }
                self::compile($stmtName,$stmtQuery,$db);
            }

        }else{
            throw new Error_Exception('stmts not in config!');
        }
        return True;
    }

    /**
     * Compile the prepared statment 
     *
     * @param String $stmtName, Statement name 
     * @param String $stmtQuery, Statement query
     * @param String $db ,Instance name of database
     *
     * @return Boolean
     */
    public static function compile($stmtName, $stmtQuery,$db ='default'){
        if(isset(self::$instances[$db][$stmtName])){ //already Compiled
            //Doing Nothing
            //Log::debug('DEALLOCATE '.$stmtName);
            DB::query(DB::UPDATE,'DEALLOCATE '.$stmtName)->execute($db);
        }
        $_ret = DB::query(DB::SELECT,$stmtQuery,False,NULL,$stmtName)->execute($db)->count();
        //Log::debug(__FUNCTION__.':compiling the pstat:'.$stmtQuery);
        self::$instances[$db][$stmtName] = time();
        return True;
    }

    /**
     * Execute the prepared statement
     *
     * @param String $stmtName, Statement Name
     * @param Array $params , The parameter to be transfered into query
     * @param Boolean $as_object, True to fetch result as object
     * @param String $db, Database Instance name
     *
     * @return Array of result set
     */

    public static function execute($stmtName,$params = array(),$as_object = TRUE,$db = 'default'){
        if(isset(self::$instances[$db][$stmtName])){
            return DB::query(DB::SELECT,NULL,$as_object,$params,$stmtName)->execute($db);
        }else{
            $_config = Pexcel::config('database')->$db;
            $_configStmts = Arr::get($_config,'stmts',NULL);
            //Compile the prepared statment 
            if(isset($_configStmts[$stmtName])){
                self::compile($stmtName,$_configStmts[$stmtName],$db);
            }else{
                return false;
            }
            return DB::query(DB::SELECT,NULL,$as_object,$params,$stmtName)->execute($db);
        }
    }
}
//该片段来自于http://outofmemory.cn