I've been down this road. See this
thread
If at all possible get off of PHP; the IDS support in PHP is bad and barely supported. Even providing a REST API to your data with Python (to IDS) and calling that from PHP is better than PHP's PDO, and especially Informix PDO, support.
It does work, but with bugs and performance issues. I am an IBM fan-boy and really respect IBM; but when they say "the PDO_INFORMIX driver is being actively maintained" I'm not certain from what parallel universe that statement is came from.
Even with a later version of IDS, good luck betting PDO_IBM to work at all. Or even finding documentation as to how.
Adam Tauno Williams
http://whitemiceconsulting.blogspot.com
