I have installed apache and php on my ubuntu 18.4 machine. php is 7.2 version and apache2 (Apache/2.4.29 (Ubuntu)). The apache server opens my website with no problem, but it can only execute the php code if it does not have a call to a function such as $_FILE. If I include $_FILE in my php code, the apache does not execute the php code and it only gives white page. Please help!