DBConnection.php

<?php

/**
 * Database Connection class.
 * 
 * Example:
 * $dbi = DBConnection::getInstance();
 * $q = "SELECT * FROM Users WHERE Username=?";
 * $a = array($_GET['username']);
 * $users = $dbi->query($q, $a);
 * if($users['count'] > 0)
 * {
 *     foreach($users['result'] as $row)
 *     {
 *         echo $row['username'] . '<br />';
 *     }
 * }
 * $dbi = null;
 * 
 * @author Chris Forrence
 * @license http://opensource.org/licenses/gpl-license.php GNU Public License
 * @version 1.0
 */
class DBConnection extends PDO
{

    private static $instance = null;
    private $connection;
    private $dbName = "db_name";
    private $dbHost = "localhost";
    private $dbUser = "db_user";
    private $dbPass = "db_pass";

    public function getConnection()
    {
        return $this->connection;
    }

    public function __construct()
    {
        try
        {
            $this->connection = new PDO("mysql:dbname=" . $this->dbName . ";host=" . $this->dbHost, $this->dbUser, $this->dbPass, array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION, PDO::ATTR_PERSISTENT => true));
        }
        catch(PDOException $e)
        {
            error_log($e->getMessage());
        }
    }

    public static function getInstance()
    {
        if(self::$instance == null || empty(self::$instance))
        {
            try
            {
                self::$instance = new DBConnection();
            }
            catch(PDOException $p)
            {
                error_log("PDOException caught: " . $p->getMessage());
            }
        }
        return self::$instance;
    }

    public function execute($query, $args = array())
    {
        $tokens = explode(" ", $query);
        try
        {
            $this->connection->beginTransaction();
            $sth = $this->connection->prepare($query);
            if(empty($args))
            {
                $sth->execute();
            }
            else
            {
                $sth->execute($args);
            }
            if(strtoupper($tokens[0]) == "SELECT")
            {
                $sth->setFetchMode(PDO::FETCH_ASSOC);
                $ret = $sth->fetchAll();
            }
            else if(strtoupper($tokens[0]) == "INSERT")
            {
                $ret = $this->getLastInsertID();
            }
            else
            {
                $ret = $sth->rowCount();
            }
            $this->connection->commit();
        }
        catch(PDOException $e)
        {
            error_log('Query failed: ' . $e->getMessage());
            error_log('Query : ' . $query);
            $this->connection->rollBack();
            $ret = -1;
        }
        return $ret;
    }

    private function getLastInsertID()
    {
        return $this->connection->lastInsertId();
    }

}