/**
* Attemps to create a PDO object based on the parameters and configured
* to throw exceptions on errors.
*
* @param string $dsn
* @param string $user
* @param string $password
* @param array $attrs = null
* @return PDO
*/
public static function getDBConn($dsn, $user, $password, array $attrs = null)
{
// First check the cache
$dbKey = md5(implode(chr(31), array($dsn, $user, $password, serialize($attrs))));
if (array_key_exists($dbKey, self::$_dbCache)) {
return self::$_dbCache[$dbKey]['db'];
}
try {
$dbConn = new PDO($dsn, $user, $password, $attrs);
$dbConn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
// Get the time zone offset
$q = <<<EOF
SELECT TIMESTAMPDIFF(
SECOND, CONVERT_TZ(NOW(), @@session.time_zone, '+00:00'), NOW()
)
EOF;
$stmt = $dbConn->query($q);
$offset = $stmt->fetchColumn();
/* This will come out as a string, which is necessary because we
need to be able to distinguish 0 and null. */
if ($offset === null) {
// This really shouldn't happen
throw new UnexpectedValueException('Got unexpected result when querying database for time ' . 'zone offset.');
}
// Now that that test is done, we can cast as an int
$offset = (int) $offset;
if (self::$_dbTimeZoneOffset === null) {
/* If this property is null, but we've already cached a
database connection, it means we've already encountered
multiple different time zone offsets. */
if (!self::$_dbCache) {
self::$_dbTimeZoneOffset = $offset;
}
} elseif (self::$_dbTimeZoneOffset !== $offset) {
self::$_dbTimeZoneOffset = null;
}
self::$_dbCache[$dbKey] = array('db' => $dbConn, 'time_zone_offset' => $offset);
return $dbConn;
} catch (PDOException $e) {
throw new RuntimeException('Caught PDOException.', null, $e);
}
}
