Anda harus "menyebutkan" semua placeholder dalam kueri Anda
$q = $this->_db->prepare("UPDATE fonds
SET Name = :name,
ContactName = :contactname,
ContactPosition = :contactposition,
ContactMail = :contactmail,
ContactPhone = :contactphone,
Website = :website
MinTic = :mintic,
MaxTic = :maxtic
WHERE id = :id");
PDO hanya menggantikan placeholder. Anda harus menambahkan placeholder itu ke kueri Anda.