what comes in the php file to mail the random mail i sent via byond?

Problem description:

In response to Nadrew (#1)
i know how to use mail() how do but i use the vars i sent via byond?
In response to Shoux Gaull (#2)

You want to focus more on the Get function.
In response to Pirion (#3)
mail($_GET["mail"],'Registrtation Test','you received a test email, you are unlucky today');

Well so if i put this script on a server like that supports php files and acsess it with world.Export(www.?????.com/php.php? it would send an email to and after that i did world export again but with other email would it send to the other email without rebooting the server?
In response to Shoux Gaull (#4)
As far as i can see that could would send the email. Each time you reload the page with the ?mail=XXX it will attempt to send another email, so no need to reboot any servers.

(also tired it with 000webhost before and I know it works with their service so no problems there either.)
In response to Pirion (#5)
thanks for the help