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I am not a coder, but I know this kind of syntax works for an include and say for a banner for example
for an include single quotes are used i.e
include('here document');
this for an echo
echo xoops_getbanner();
With custom blocks you don't include the phptags, but you may know that already
If you post more of the code you are using perhaps a coder/developer will pick up on it..