private static $_connectionLink = null;
private static $_connectionErrors = null;

public function __construct() {
    if (empty(self::$_connectionLink)) {
        self::connect();
        $handle = fopen('connect.log','a');
        fputs($handle,"----------- NEW connect ".date('Y-m-d H:i')."----------- n");
        fclose($handle);
    }
}
    private static function connect() {
    $host = 'localhost';
    $user = 'user';
    $password = 'pass';
    $dbName = 'dbname';

    self::$_connectionLink = @mysqli_connect($host,$user,$password,$dbName);
    if (!mysqli_connect_errno()) {
        mysqli_set_charset(self::$_connectionLink, 'utf8');
    } else {

    }
}