[Staffslug] PHP - Apache 2

Hi, Can anyone tell me why PHP5 suddenly refuses to interpret embedded php code in an html document? I am completely baffled by this one. Nothing has changed. HTML docs are delivered correctly, PHP documents as well but code in an HTML doc with <?php .....?> is ignored. If you check 'view source code' from the browser its all there including the php stuff. I should be grateful for any pointers you might suggest. Walter