PHP Include from another Site

Hi, I have been looking for a couple of days on and off, but I can’t find anything that answers this question. Any help would be appreciated.

I want to have content central to several sites to be accessible or Included via (PHP Include or other mechanism) but everything I’ve tried isn’t working. The most promising effort to put the fully qualified address in the include statement causes the site to reset. When it happened the first time it bothered me, but then I got used to is after a few dozen times.

On the local site in the local directory, this statement works fine:
<?php include(‘AntioxidantsAthleticPerf.txt’); ?>

On the satellite site same file … below path … every type of call … get_template, include, etc … server reset and it just won’t work.

<?php include(‘https://[source site]/[path]/AntioxidantsAthleticPerf.txt’); ?>

I am not sure if the files should be .php or .html or .txt because is is on a remote host … I have tried them all with no success. It has become a mission to figure this out, but if it doesn’t work then … let me know and I will find another way.

Thanks.