class Conexion{

	protected $_lastid;
	protected $host;
	protected $username;
	protected $password;
	protected $dbname;

	function Conexion(){
		$config = Zend_Registry::getInstance();
		$this->host = ['host'];
		$this->username = ['username'];
		$this->password = ['password'];
		$this->dbname = ['dbname'];
	}

	public function getID()
	{
		return $this->_lastid;
	}

	function transaccion($query,$encodeJSON=false,$encode=false){

		$conexion = @mysql_connect($this->host, $this->username, $this->password);

		@mysql_select_db($this->dbname, $conexion);

		if($encode)
		{
			$executeQueryUTF8Format = @mysql_query('SET NAMES utf8;');
		}

		if( $conexion == false ){	return false;	}

		/* Begin transaction. */
		$begin = @mysql_query("BEGIN;");

		/* Execute operations that are part of the transaction. Commit on
		 success, roll back on failure. */
		$executeQuery = @mysql_query($query);

		$this->_lastid= @mysql_insert_id();

		//If commit fails, roll back the transaction.
		$commit = @mysql_query("COMMIT;");

		if ($begin && $executeQuery && $commit){

			$data = array();

			while ($row=@mysql_fetch_object($executeQuery)){
				$data [] = $row;
			}

			// Liberar resultados
			@mysql_free_result($begin);
			@mysql_free_result($executeQuery);
			@mysql_free_result($commit);

			// Cerrar la conexi�n
			@mysql_close($conexion);

			if($encodeJSON)
			return json_encode($data);
			else
			return $data;

		}else{
			@mysql_query("ROLLBACK");

			// Liberar resultados
			@mysql_free_result($begin);
			@mysql_free_result($executeQuery);
			@mysql_free_result($commit);

			// Cerrar la conexión
			@mysql_close($conexion);

			return false;
		}
	}

}

se usa asi $this->conexion->transaccion("consulta",false,true);//devuelve un array si pone true en el segundo parametro devuelve un json