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Groups > comp.lang.php > #1858

Re: database access

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On 5/26/2011 12:07 PM, sheldonlg wrote:
> On 5/26/2011 11:41 AM, Jerry Stuckle wrote:
>> On 5/26/2011 10:22 AM, sheldonlg wrote:
>>> 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.
>>>
>>
>> A better way would be to pass the basic information to the constructor -
>> i.e. the host, userid, password and database name. Let the constructor
>> build the database object. That way it is completely encapsulated and
>> the rest of the program is not dependent on a database object. If he
>> later finds he wants to change database objects (i.e. maybe PDO is to
>> slow and he wants to use mysqli), he can do so without changing anything
>> in the rest of the program. The class is now more fully encapsulated.
>>
>> A very good reason for not passing it to the constructor.
>
> Good point. It would be best to pass those three instead. Point was that
> I was making is that it is best to pass what is _ALWAYS_ needed through
> the constructor. Your suggestion is better.
>
four, not three.

-- 
Shelly

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database access Jivanmukta <jivanmukta@poczta.onet.pl> - 2011-05-25 10:17 -0700
  Re: database access Jerry Stuckle <jstucklex@attglobal.net> - 2011-05-25 17:37 -0400
    Re: database access sheldonlg <sheldonlg@thevillages.net> - 2011-05-26 08:09 -0400
      Re: database access Jerry Stuckle <jstucklex@attglobal.net> - 2011-05-26 09:00 -0400
        Re: database access sheldonlg <sheldonlg@thevillages.net> - 2011-05-26 10:22 -0400
          Re: database access Jerry Stuckle <jstucklex@attglobal.net> - 2011-05-26 11:41 -0400
            Re: database access sheldonlg <sheldonlg@thevillages.net> - 2011-05-26 12:07 -0400
              Re: database access sheldonlg <sheldonlg@thevillages.net> - 2011-05-26 12:14 -0400
    Re: database access sophal chao <w3cyberlearning@gmail.com> - 2011-05-29 13:41 -0700
      Re: database access Jerry Stuckle <jstucklex@attglobal.net> - 2011-05-29 23:12 -0400
  Re: database access JohnT <john@example.com> - 2011-05-26 13:05 +0000
    Re: database access Jivanmukta <jivanmukta@poczta.onet.pl> - 2011-05-26 06:37 -0700
      Re: database access sheldonlg <sheldonlg@thevillages.net> - 2011-05-26 10:30 -0400
        Re: database access sheldonlg <sheldonlg@thevillages.net> - 2011-05-26 10:33 -0400
      Re: database access Jerry Stuckle <jstucklex@attglobal.net> - 2011-05-26 11:43 -0400
    Re: database access Michael Fesser <netizen@gmx.de> - 2011-05-26 19:48 +0200
      Re: database access Erwin Moller <Since_humans_read_this_I_am_spammed_too_much@spamyourself.com> - 2011-05-30 10:56 +0200

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