Logs the IP of the visitor who runs the script to a .txt file. Useful when you don't have a dynamic DNS and need to access your home network / Raspberry Pi.

Example Usage:

crontab -e

Update IP every hour (= 'at minute 0')

0 * * * * curl http://urlofyourhost.com/ip.php

The logged ip will then be written to 'ip.txt' (located in the same folder as ip.php)