Thread:Project:Support desk/extraneous text at top of page

Hi,

How can I stop some extraneous text from showing at the top of every page on my new installation of wikimedia onto Debian mint 15 using synaptics?

MediaWiki	1.19.7+dfsg-1 PHP	5.5.1-2 (apache2handler) MySQL	5.5.31-1

The text showing is from some php code prepended to the page, as shown in the page source below, it starts with "Wikidiff2" (i.e. after the first closing angle bracket) and flows up to the DOCTYPE tag.

The page source: