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1. When using PDO, you want to get the benefits of automatic parameter escaping. By wrapping your PDO class you are limiting it's functionality. Check out this question for a better example:

http://stackoverflow.com/questions/6366661/php-pdo-parameterised-query-for-mysql

2. Every time you run a query you are making a new PDO instance. It might be better to have an application resource pool that you can call to get a preconfigured db handle.

3. You wrote some sql to be able to fetch a stock by ID, that should probably be functionality that is reusable.

combining 1 & 2 & 3 .. code would probably look better as something like this:

class ApplicationResourcePool 
{
 static var $_dbHandle;
 private static $_dbConfig = array(
 'dsn' => '',
 'username' => '',
 'password' => '',
 );
 public static getDbHandle(){
 if(self::$_dbHandle == null){
 self::$_dbHandle = new PDO(
 self::$_dbConfig['dsn'] , 
 self::$_dbConfig['username'], 
 self::$_dbConfig['password'] 
 );
 }
 return self::$_dbHandle;
 }
}
class StockMapper
{
 protected $_dbh; 
 public __construct($dbh = null)
 {
 if($dbh == null){
 $this->_dbh = ApplicationResourcePool::getDbHandle();
 } else {
 $this->_dbh = $dbh;
 }
 
 }
 public getStockById($stockId){
 
 $sth=$this->_dbh->prepare("SELECT * from stock WHERE id = :stockId"); 
 $sth->bindParam(":stockId", $stockId);
 $sth->execute();
 $result = $sth->fetch(PDO::FETCH_ASSOC);
 return $result[0];
 }
}

your codeBlock then becomes:

$stockMapper = new StockMapper();
$stockData = $stockMapper->getStockById('302');

1. When using PDO, you want to get the benefits of automatic parameter escaping. By wrapping your PDO class you are limiting it's functionality. Check out this question for a better example:

https://stackoverflow.com/questions/6366661/php-pdo-parameterised-query-for-mysql

2. Every time you run a query you are making a new PDO instance. It might be better to have an application resource pool that you can call to get a preconfigured db handle.

3. You wrote some sql to be able to fetch a stock by ID, that should probably be functionality that is reusable.

combining 1 & 2 & 3 .. code would probably look better as something like this:

class ApplicationResourcePool 
{
 static var $_dbHandle;
 private static $_dbConfig = array(
 'dsn' => '',
 'username' => '',
 'password' => '',
 );
 public static getDbHandle(){
 if(self::$_dbHandle == null){
 self::$_dbHandle = new PDO(
 self::$_dbConfig['dsn'] , 
 self::$_dbConfig['username'], 
 self::$_dbConfig['password'] 
 );
 }
 return self::$_dbHandle;
 }
}
class StockMapper
{
 protected $_dbh; 
 public __construct($dbh = null)
 {
 if($dbh == null){
 $this->_dbh = ApplicationResourcePool::getDbHandle();
 } else {
 $this->_dbh = $dbh;
 }
 
 }
 public getStockById($stockId){
 
 $sth=$this->_dbh->prepare("SELECT * from stock WHERE id = :stockId"); 
 $sth->bindParam(":stockId", $stockId);
 $sth->execute();
 $result = $sth->fetch(PDO::FETCH_ASSOC);
 return $result[0];
 }
}

your codeBlock then becomes:

$stockMapper = new StockMapper();
$stockData = $stockMapper->getStockById('302');