adding html code produced by a php program to various template in 3.8.4

[sailnet]

I would like to include some html generated by a php program I wrote into various templates on my php site.

I assume I have to get it assigned to a $variable-name and just include $variable-name in the templates where I want this html included.

what's the best way to go about this?

thanks in advance.

ps: I do not want to insert the html into the various templates because the php program generates an iframe with a veriable height based on how much content is pass it.