desperate: my 'what is my public ip address' tool keeps showing localhost, help fix this!

i'm completely pulling my hair out trying to fix our 'what is my ip address' tool. it's supposed to show a user's *public IP address*, but for a significant chunk of users, it's returning '127.0.0.1' or 'localhost'. this is driving me nuts. it's causing so much frustration for our users and me trying to debug this client ip detection problem.

• The Core Problem: Our tool, designed to simply display a user's public IP, is incorrectly showing internal IPs (localhost/127.0.0.1) for many visitors.
• Current Setup:
  • it's a simple PHP script running on an Nginx server.
  • we're primarily using $_SERVER['REMOTE_ADDR'] and trying various X-Forwarded-For or CF-Connecting-IP headers if available.
  • hosted on a VPS, not behind Cloudflare directly (though users might be).
• What I've Tried (and Failed At):
  • checked Nginx config for proper proxy pass settings (it's not proxied by us directly).
  • logged all $_SERVER variables to see what headers are actually coming through – sometimes X-Forwarded-For is missing or empty.
  • tested with different VPNs and ISPs myself; sometimes it works, sometimes it doesn't even for me.
  • even tried a fallback to an external API (like ipify) but want to avoid that for speed/cost.
• Specific Observations:
  • seems to happen more often with mobile users or certain ISPs.
  • it's not 100% of the time, which makes it super hard to debug.
  • when it shows localhost, it's definitely not the *actual* public IP they're browsing from.
• My Desperate Plea:
  • what am i missing? is there some common server configuration or PHP setting that could cause this?
  • how do other 'what is my ip' sites reliably get the *true* public IP even when behind proxies or weird network setups? this client ip detection needs to be reliable.
  • any Nginx configurations or PHP snippets i should be looking at?

thanks in advance, i'm seriously stuck here!