Question

I built this class to work with PDO, to make SQL queries ‘easier’ and less to worry about.

Here are my thoughts

• Should it be more like class DB extends PDO?
• Is the query method too big? Should it be split into private methods which are called.. is this what is known as loose coupling?
• Is my way for detecting a SELECT query too ugly for it’s own good?
• What other problems are evident? As I am sort of learning-as-I-go, I’m sure I could have overlooked a lot of potential problems.

Thank you

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 class Db  {     private static $_instance = NULL;       private function __construct() {          // can not call me     }      private function __clone() {          // no!     }      public static function getInstance() {          if (!self::$_instance)         {              try {                  self::$_instance = new PDO('mysql:host=' . CONFIG_MYSQL_SERVER . ';dbname=' . CONFIG_MYSQL_DATABASE, CONFIG_MYSQL_USERNAME, CONFIG_MYSQL_PASSWORD);;                 self::$_instance-> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);              } catch(PDOException $e) {                  trigger_error($e->getMessage());              }          }          return self::$_instance;       }        public static function query($query /*string*/, $bindings = NULL)     {          $queryPortion = substr($query,0, 6);          try {              if ($bindings) {                      $prepared = self::getInstance()->prepare($query);                      foreach($bindings as $binding=>$data) { // defaults to string                          if (!is_array($data)) {                             $prepared->bindParam($binding, $data);                           } else {                              switch(count($data)) {                                  case 1:                                     $prepared->bindParam($binding, $data['value']);                                     break;                                                            case 2:                                     $prepared->bindParam($binding, $data['value'], $data['dataType']);                                     break;                                  case 3:                                     $prepared->bindParam($binding, $data['value'], $data['dataType'], (int)$data['length']);                                     break;                                                            default:                                     trigger_error('An error has occured with the prepared statement bindings.');                                     return false;                                     break;                             }                         }                      }                      $prepared->execute();                      return $prepared->fetchAll(PDO::FETCH_ASSOC);               } else if (String::match($queryPortion, 'select')) { // if this is a select query                  $rows = self::getInstance()->query($query);                  return $rows->fetchAll(PDO::FETCH_ASSOC);              } else {                  return self::getInstance()->exec($query);              }           }          catch(PDOException $e)         {             trigger_error($e->getMessage());         }       }      public static function getLastInsertId()     {         try {             self::getInstance()->lastInsertId();           }         catch(PDOException $e)         {             trigger_error($e->getMessage());         }      }      public static function disconnect()     {         // kill PDO object         self::$_instance = NULL;      }  } 

Answer 1

It’s not bad and as it’s been said it might help for small applications although it’s mostly a very thin abstraction on another abstraction. It’s not bringing a lot of others functionalities.

Something you might want to consider, amongst other things:

• As this is PHP5 code, use exceptions instead of trigger_error and set_exception_handler if necessary until exceptions are more widespread, but it’s definitely cleaner and more future-proof.
• You are using a singleton, it’s not a bad thing necessarily but in this case, for example, one shortcoming will be that you’ll only be able to handle one connection to one database.
• I don’t know if you make use of stored procedures, but a stored procedure might return a result set through the query() method too.
• You have two semi-colons (;;) at the end of your new PDO line.

That being said, I don’t think your query method is too big and there’s not much that could be recalled from elsewhere in there at the moment. Though as soon as you see two or three lines that could be called from another function, split it. That’s a good way to DRY.