I am working with a colleague to set up their local environment on a MAC in XAMPP, on windows my vhost looks like the one below.
When I access a URL like http://domain.l
Do you know whether PHP is running as a CGI program or as a webserver module? You should be able to find this out if you can get a phpinfo() page working (maybe from a regular folder inside the website root). If you're running as a webserver module then you should have a section near the top with a heading of Server API which says Apache 2.0 Handler (or equivalent).
From these pages:
... it seems that it may be either due to PHP running as a CGI script, or else a conflict between PHP and another CGI handler.
One of the posters on the third linked page found that their similar-sounding end of script headers issue was resolved by removing / commenting out the Options +ExecCGI line in their .htconfig / vhosts file.
Might be worth having a read through the above links to see if your problem is related.