I would like to add an extra field to the order page so a company can add their company name.
I looked at Extra Checkout Fields section but this doesn't look like what I need. PHP version.

Extra checkout fields

It is possible to add two new fields to your cart checkout page. The extraorderfield1 will go at the top of the billing and shipping form and the extraordefield2 at the bottom of the billing and shipping form.

$extraorderfield1="Company Name"; - adds a company name field to the top of your cart checkout page, text can be edited here for other uses.