I have never used Portals with PHP.
I don't think that it is possible to generate this with PHP Assistant (but I'm not sure - I haven't test that).
Make a new calculation field to get a list from Parents portal records.
And this calculation field is possible to include in PHP.
And this must speed up data displaying.
Thanks for the tip. It worked well after I tweaked a bit. And, I learned about the List calculation.