Making PDO Database Connection available in controllers and models - mysql

Question

right now, I am kinda frustrated and I hope someone can help me and point me into the right direction.
I have an "old" project which uses the mysql statements for connection to database, etc.
Within this project I have the following:
An index file containing
*
* load configuration and connect to database
*/
$projectConfiguration = new projectConfiguration();
$dbconnect = $projectConfiguration->connect($projectConfiguration->databaseHost, $projectConfiguration->databaseName, $projectConfiguration->databaseUser, $projectConfiguration->databasePass);
// load controller
$ReqMod = FatFramework\Functions::getRequestParameter("mod");
if (!$ReqMod) {
$ReqMod = FatFramework\Functions::getRequestParameter("controller");
}
$module = ($ReqMod) ? $ReqMod : 'default';
In this style I call the views and actions in classes, like SaveAction()
Using mysql always made it very simple to use this database connection in the models called by the controllers like
public function loadCustomersList($sAdditionalWhere = false)
{
$sQuery = "SELECT * FROM customers WHERE 1 ";
if ($sAdditionalWhere) {
$sQuery .= "AND " . $sAdditionalWhere . " ";
}
$sQuery .= "ORDER BY company";
$sql = mysql_query($sQuery);
while (($customer = mysql_fetch_object($sql)) != false) {
$aCustomers[] = $customer;
}
return $aCustomers;
}
I want to totally refractor this project and use PDO. I tried for the last 4 hours to find a solution, but I can't figure out how to make it work.
I think I don't need an extra dbconnect class since PDO is a class itself, am I right?
In the new index file I tried the following:
$db = new database();
try{
$dbc = new PDO($db->get_DbConSettings());
$dbc->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}catch(PDOException $e)
{
echo 'Verbindung fehlgeschlagen: '.$e->getMessage();
}
But with this $dbc will not available in controllers or models. It there a way to make it available there? If not, what is the best solution?
Do I have to make a database connection in every model?
An other issue I have with this is:
$db->get_DbConSettings()
in
$dbc = new PDO
gives back
'mysql:host=127.0.0.1; dbname=c1virtbkk', 'root', '123'
($dbc = new PDO('mysql:host=127.0.0.1; dbname=c1virtbkk', 'root', '123');)
I cannot connect to the database. I get the following:
Verbindung fehlgeschlagen: could not find driver
If I don't use $db->get_DbConSettings and put the required information manually in, I don't get any error and can do queries. Any hints?
Help is really appreciated.
Thanks in advance!
Mark

Answer 1

Definitely don't create a new PDO connection in each model. Creating MySQL database connections is fairly quick, but there's still some overhead to doing so. You want to reuse a connection throughout your request. If nothing else, it allows you to share a transaction across multiple models.
Some frameworks store shared resource objects in a "registry" class which is a singleton key-value store. It's not really much more than a global hash array, but making it a class makes the registry itself more easily tested with PHPUnit. See https://framework.zend.com/manual/1.12/en/zend.registry.using.html for an example of a registry.
You're right that PDO is a class, even though it's implemented as a C extension instead of a PHP class. But it's a class, and new PDO(...) returns an object of that class.
One reason to create a db class of your own is to help you in unit-testing, because you could create a mock object for your db class so you can test your other classes (even model classes) without needing a live database connection. Your db class could extend or else contain a PDO object.
Your issue about the error "could not find driver" is probably because the PDO driver for mysql is not installed. PDO is one PHP extension, and then there's a separate extension for each brand of SQL database. You can confirm this with:
$ php -i
...lots of output...
PDO
PDO support => enabled
PDO drivers => mysql, odbc, sqlite
pdo_mysql
PDO Driver for MySQL => enabled
Client API version => mysqlnd 5.0.11-dev - 20120503 - $Id: 76b08b24596e12d4553bd41fc93cccd5bac2fe7a $
...more output for other extensions...
Note that PDO tells me which drivers I have installed: mysql, odbc, and sqlite.
So you need to install pdo_mysql. I'm not sure what OS you're on, but I'm often on CentOS Linux or Ubuntu Linux. The pdo_mysql is available as a separate package via yum or apt.
Re your comment:
Okay, here's an example of a registry:
class registry {
protected static $items = array();
public static get($key) {
return isset(self::$items[$key])?
self::$items[$key] : null;
}
public static set($key, $object) {
self::$items[$key] = $object;
}
}
In your controller initial code, you'd create a database object and store it in the registry:
$projectConfiguration = new projectConfiguration();
$dbconnect = $projectConfiguration->connect(
$projectConfiguration->databaseHost,
$projectConfiguration->databaseName,
$projectConfiguration->databaseUser,
$projectConfiguration->databasePass);
registry::set('db', $dbconnect);
Then in your model class methods (or anywhere you need the database), get the db object from the registry and use it:
public function loadCustomersList($sAdditionalWhere = false)
{
$sQuery = "SELECT * FROM customers WHERE 1 ";
if ($sAdditionalWhere) {
$sQuery .= "AND " . $sAdditionalWhere . " ";
}
$sQuery .= "ORDER BY company";
$db = registry::get('db');
$stmt = $db->query($sQuery);
$aCustomers = $stmt->fetchAll(PDO::FETCH_ASSOC);
return $aCustomers;
}