Minecraft server automatic startup and shutdown

Install the .php file on a webserver and configure the variables as desired.

Place the remaining files on a server with CRON (could be the same server, just not inside the web folder) and run the shell script every 5 minutes:

*/5 * * * * * /your/path/here/minecraftautoshutdown.sh

Ensure the same password is present in the php script and the shutdown script.

Call the php script via HTTP using the correct password when players want to play:

curl http://your.webserver.here/minecraft.php?action=on&password=your_password_here

If the CRON job runs properly and has all the right variables/permissions/dependencies, it will shut down the DO droplet about 30-40 minutes after no players are detected in the game.