Hello and welcome to 4images forum.
First of all, there shouldn't be any php.html template.
Secondly, check in settings and make sure there is no .php extension in "Valid file extensions" list.
Then in ACP (Admin Control Panel) -> Edit images, search for *.php* in filename field (not image name), make sure you include asteriks *. If it finds any "images" with .php extension, download these files to your computer for further investigation to make sure they are not harmful and then delete them from your website. Then scan your entire webspace for any suspicious files.