Rider:
addon_1stpagenews2.php
I suppose default filename doesn't contain the number on its end, that's why at first you may consider to upgrade to the newest version of this add-on.
Answering your question, if you include via PHP, then the original of this script should contain:
$excludeIncludes=FALSE;
but the duplicate should contain:
$excludeIncludes=TRUE;
Obviusly the error appears because the script tries to load some other scripts and functions twice. Setting up this option you will force only the first script make inclusions, but not the second.