The documentation needs to clarify the distinct between the PHP db2 drivers as there is two one being "nts" and the other "ts". It is not obvious this relates to "thread safe". Point of confusion for installer who has little knowledge of PHP. May be the documentation should suggest which one to choose and why. DBAs installing the product will have very little knowledge of PHP and in many cases don't want to acquire knowledge.
If latest ZEND Community edition is used then install very simple as it provides option to auto install db2 drivers.