Single Database Object in PHP 5 Using the Singleton Pattern

<?php
/*

Calling the call() method statically will give you access to the MySQLi methods.

Whenever you need to make a query, you just have to do this:

$result = Database::call()->query("SELECT * FROM ...");

*/
class Database
{
	const MYSQL_HOST = "";
	const MYSQL_USER = "";
	const MYSQL_PASS = "";
	const MYSQL_DB = "";
	
	private static $instance; // stores the MySQLi instance
	
	private function __construct() { } // block directly instantiating
	
	private function __clone() { } // block cloning of the object
	
	public static function call()
	{
		// create the instance if it does not exist
		if(!isset(self::$instance))
		{
			// the MYSQL_* constants should be set to or
			//  replaced with your db connection details
			self::$instance = new MySQLi(self::MYSQL_HOST, self::MYSQL_USER, self::MYSQL_PASS, self::MYSQL_DB);
			if(self::$instance->connect_error)
			{
				throw new Exception('MySQL connection failed: ' . self::$instance->connect_error);
			}
		}
		// return the instance
		return self::$instance;
	}
}
?>