Well, you can write such a process in your language of choice. Since you've already got PHP & SQL interfaced though, you could cheat and create another page for the arduino to GET periodically. Have the alert queries run from there.
Well, you can write such a process in your language of choice. Since you've already got PHP & SQL interfaced though, you could cheat and create another page for the arduino to GET periodically. Have the alert queries run from there.