why php function in some location, but not other ??

Hi mates,

Look I have some serious issue in here. when I go to a folder that contain index.php, the full php code shows up plain instead of being hidden since it is the php property to hide whatever inside it. for example, when I go to any of my domain folder like this domain.com/app/ the code shows up as a plain code while it is supposed to be hidden… or it should search for index.php or index.html…, but it doesn’t.

However, when I go to the same folder and I write domain.com/app/index.php… this way it works and only this way, which is high risk since a hacker can see my php content and break into my site easily…

anyone knows how to fix this issue??

Thanks