Closing my mySQL connection - php

Question

I'm a .Net developer that have taken over a PHP project. This project has a database layer that looks like this:
<?php
class DatabaseManager {
private static $connection;
const host = "projectname.mysql.hostname.se";
const database = "databaseName";
const username = "userName";
const password = "password";
public function __construct()
{
}
public function instance($_host = null, $_username = null, $_password = null)
{
if(!self::$connection)
{
if(!$_host || !$_username || !$_password)
{
$host = self::host;
$username = self::username;
$password = self::password;
}else{
$host = $_host;
$username = $_username;
$password = $_password;
}
self::$connection = mysql_connect($host, $username, $password);
$this->setDatabase();
}
return self::$connection;
}
public function setDatabase($_database = null)
{
if(!$_database)
{
$database = self::database;
}else{
$database = $_database;
}
$connection = $this->instance();
mysql_select_db($database, $connection) or die(mysql_error());
}
} ?>
I have written a php file that uses this layer but after a while i got these mysql errors implying i didn't close my connections which i hadn't. I try to close them but know i get other weird errors like system error: 111. Very simplyfied my php file looks like this:
<?php
$return = new stdClass();
$uid = '9999999999999';
$return->{"myUid"} = $uid;
$dm = new DatabaseManager();
$dmInstance = $dm->instance();
/* MY CLICKS */
$sql = sprintf("SELECT count(*) as myClicks FROM clicks2011, users2011 WHERE clicks2011.uid = users2011.uid AND users2011.uid = %s AND DATEDIFF(DATE(at), '%s') = 0 AND exclude = 0", mysql_real_escape_string($uid), mysql_real_escape_string($selectedDay));
$result = mysql_query($sql, $dmInstance) or die (mysql_error());
$dbResult = mysql_fetch_row($result);
$return->{"myClicks"} = $dbResult[0];
mysql_close($dmInstance);
echo json_encode($return); ?>

Answer 1

Okay, I'm going to post this as an answer because I think one (possibly both) of these things will help you.
First: You don't need to manually close your MySQL connections. Unless you have set them up so that they persist, they will close automatically. I would avoid doing that unless you determine that every other problem is NOT the solution.
In addition, I would switch to using prepared statements. It's more secure, and pretty future-proof. I prefer PHP's PDO over mysqli, but that's up to you.
If you'd like to look over an example of a simple PDO object to take the many lines out of creating prepared statements and connections and getting results, you can look at my homebrew solution.
Second: "System Error 111" is a MySQL error. From what I've read, it appears that this error typically occurs when you are using PHP and MySQL on the same server, but telling PHP to connect to MySQL via an IP address. Switch your $host variable to 'localhost'. It is likely that this will solve that error.

Answer 2

The problem here is you're calling mysql_close and not specifying a valid mysql connection resource object. You're, instead, trying to close an instance of the DatabaseManager object.
You'll probably want to run mysql_close(DatabaseManager::connection); which is where the DatabaseManager is storing the resource object.
Additionally, I'd personally recommend you learn PDO or use the mysqli drivers. In future releases of PHP the built in mysql functions will be moved into E_DEPRECATED

Answer 3

Try implement __destrcut
public function __destruct()
{
mysql_close(self::$connection)
}
Then simply use unset($dm);