imagecreatefromjpeg and similar functions are not working in PHP

Question

I’ve searched for this and the solutions provided in past questions are completely incomprehensible to me. Whenever I run functions like imagecreatefromjpeg, I

Answer 1

As mentioned before, you might need GD library installed.

On a shell, check your php version first:
php -v

Then install accordingly. In my system (Linux-Ubuntu) it's php version 7.0:
sudo apt-get install php7.0-gd

Restart your webserver:
systemctl restart apache2

You should now have GD library installed and enabled.