class SQLStatement {
	private $statement = "";
	public function __construct($statement) {
		$this->statement = $statement;
	}
	public function getStatement() {
		return $this->statement;
	}
}

class DBUtilities {
	static public function einfuegen($wert) {
		return new SQLStatement("INSERT INTO ... VALUES ($wert)");
	}
}

$db->query(DBUtilities::einfuegen("Hallo Welt")->getStatement());