Todd, you didn't say which weather software package you're using.
If it's VWS, then you need to pick a nearby METAR as your first entry to set the condition icon for your station.. that will be picked up by the ^climate_cconds1^ variable, and interpreted by the $vws_icon lookup to pick the right icon to use.
If you're using Weather-Display, then you should us the clientraw.txt file as the data source, and it will have the icon to use.
If you're using WeatherLink or another package, then the condition icon is not available, since the packages don't produce one
BTW.. it would help if you updated your profile to include your weather software used and a link to the homepage of your weather website
As for why mb_convert_case seems to be missing in your PHP, that's definitely a thing to take up with your ISP.
Best regards,
Ken