I'm getting my daughter an emergency alert bracelet because we're traveling across the US soon. On the bracelet I'm getting my website address for the person who finds/kidnaps my kid.
When every ANYONE visits the unique URL, I want it to register their IP, and as much other personally identifying data as possible, then send that to me as an email.
This should tell me where they are located at a bare minimum, but in the even that they are criminals, I'd like to have enough information to help the police track them down faster.
I was thinking a $_SERVER dump via PHP, and possibly some tricky JavaScript methods.
What specifically should I implement using PHP and Javascript to track down the visitor?
The reason why web applications are blowing up is because how secure they are. Browsers unfortunately will not give you access to much information, however you can access their IP address and Geolocation.
I think the most data you will be able to get is their Long/Lat and IP address, however they would need to allow the site to grab their Geolocation.