| Re: database access [message #174199 is a reply to message #174196] |
Thu, 26 May 2011 14:22   |
sheldonlg
Messages: 166
Registered: September 2010
Karma:
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Senior Member |
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On 5/26/2011 9:00 AM, Jerry Stuckle wrote:
> On 5/26/2011 8:09 AM, sheldonlg wrote:
>> On 5/25/2011 5:37 PM, Jerry Stuckle wrote:
>>> On 5/25/2011 1:17 PM, Jivanmukta wrote:
>>>> I new relatively new to PHP. I need your opinion if the following set
>>>> of database functions make sense:
>>>>
>>>> function openDatabase() {
>>>> global $db;
>>>> try {
>>>> $db = new PDO('mysql:host=' . MYSQL_SERVER . ';dbname=' .
>>>> MYSQL_DATABASE, MYSQL_USER, MYSQL_PASSWORD);
>>>> $db->exec('SET NAMES latin2');
>>>> $db->exec('SET CHARACTER SET latin2 COLLATE latin2_general_ci');
>>>> $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
>>>> register_shutdown_function('closeDatabase');
>>>> } catch (PDOException $e) {
>>>> return false;
>>>> }
>>>> return true;
>>>> }
>>>>
>>>> function closeDatabase() {
>>>> global $db, $inTransaction;
>>>> if ($inTransaction) {
>>>> $db->rollBack();
>>>> $inTransaction = false;
>>>> }
>>>> if (!is_null($db)) {
>>>> $db = null;
>>>> }
>>>> }
>>>>
>>>> function queryDatabase($sql) {
>>>> global $db, $inTransaction;
>>>> $result = array();
>>>> try {
>>>> $qry = $db->query($sql);
>>>> if (!empty($qry)) {
>>>> $result = $qry->fetchAll();
>>>> }
>>>> } catch (PDOException $e) {
>>>> if ($inTransaction) {
>>>> $db->rollBack();
>>>> }
>>>> error(ERRMSG_DATABASE_OPERATION_FAILED);
>>>> }
>>>> return $result;
>>>> }
>>>>
>>>> function execDatabase($sql) {
>>>> global $db, $inTransaction;
>>>> $result = array();
>>>> try {
>>>> $result = $db->exec($sql);
>>>> } catch (PDOException $e) {
>>>> if ($inTransaction) {
>>>> $db->rollBack();
>>>> }
>>>> error(ERRMSG_DATABASE_OPERATION_FAILED);
>>>> }
>>>> return $result;
>>>> }
>>>>
>>>> function startTransaction() {
>>>> global $db, $inTransaction;
>>>> $db->beginTransaction();
>>>> $inTransaction = true;
>>>> }
>>>>
>>>> function commitTransaction() {
>>>> global $db, $inTransaction;
>>>> $inTransaction = false;
>>>> if ($db->commit()) {
>>>> return;
>>>> }
>>>> $db->rollBack();
>>>> error(ERRMSG_DATABASE_OPERATION_FAILED);
>>>> }
>>>>
>>>> function rollbackTransaction() {
>>>> global $db, $inTransaction;
>>>> $inTransaction = false;
>>>> if ($db->rollBack()) {
>>>> return;
>>>> }
>>>> error(ERRMSG_DATABASE_OPERATION_FAILED);
>>>> }
>>>>
>>>> function lockTables($tables) {
>>>> return execDatabase('LOCK TABLES ' . join(' WRITE, ', $tables) . '
>>>> WRITE');
>>>> }
>>>>
>>>> function unlockTables() {
>>>> return execDatabase('UNLOCK TABLES');
>>>> }
>>>
>>> Kind of, and maybe a bit overkill. But personally I'd put it all in a
>>> Database class. The code would be more flexible and less prone to
>>> errors.
>>>
>>
>> Further, I would not have globals. I would pass $db in via the
>> constructor. Likewise, I would have $inTransaction be a class variable
>> which gets set by the method startTransaction().
>>
>
> That was part of the class, Sheldon. In fact, I wouldn't even pass $db
> into the constructor; it (along with $inTransaction, as you note) would
> be class variables. That way the rest of the program is completely
> independent of the database (and you can have more than one database
> active concurrently if you want).
If you don't pass it in with the constructor, then you need something
like a setDb($parameter) to set the class variable. Passing it along
with the constructor does not limit you to only one database
concurrently. After all, you could readily do
$dbObj1 = new DatabaseClass($db1);
$dbObj2 = new DatabaseClass($db2);
What passing it along inside the constructor does is (a) it saves a line
of code each time in the invocation process(es) and (b) uniquely
identifies a particular instance of the class. Since the DatabaseClass
_MUST_ have the db defined, there is no problem with passing it in with
the constructor and no reason not to do so.
--
Shelly
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