Generally you will not be able to retrieve the local ip address of any computer that resides behind a NAT router / firewall and especially not with PHP which runs at the server anyway so the code above would find the ip of the server.
However you can use Javascript and a feature found in webRTC to reveal the local IP address of a visitor to your portal. The result of which can be passed to PHP using Ajax if required. I discovered this a few weeks ago whilst investigating a connectivity issue - a site I visited was showing my public & local ip addresses. After looking at the source code and doing further research I put the following little function together - perhaps it may be of use.
<?php
?>
<!doctype html>
<html>
<head>
<meta charset='utf-8' />
<title>Get Local IP address</title>
<script>
const rtcpip=function( server, callback ){
/*
https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/createDataChannel
https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/createOffer
*/
let debug=true;
let oList={
google1:'stun1.l.google.com:19302',
google2:'stun2.l.google.com:19302',
google3:'stun3.l.google.com:19302',
google4:'stun4.l.google.com:19302',
kundenserver:'stun.kundenserver.de:3478',
mozilla:'stun.services.mozilla.com:3478',
notts:'stun.nottingham.ac.uk:3478'
};
const getserver=function(){
return oList.hasOwnProperty( server ) ? oList[ server ] : oList.mozilla;
};
let duplicates={};
let stunsvr=getserver();
let RTCPeerConnection=window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;
let oConstraints={ optional: [ { RtpDataChannels: true } ] };
let oServers = { iceServers: [ { urls: 'stun:' + stunsvr } ] };
const info=function(m){
if( arguments.length==1 && debug )console.info(m);
if( arguments.length==2 && debug )console.info(m,arguments[1]);
};
const candidatehandler=function( candidate ){
info( candidate );
let regex = /([0-9]{1,3}(\.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/
let addr = regex.exec( candidate )[1];
if( duplicates[ addr ] === undefined ) callback( addr );
duplicates[ addr ] = true;
};
const icelistener=function( oIce ){
if( oIce.candidate ) candidatehandler.call( this, oIce.candidate.candidate );
};
const icedclistener=function(e){
let oChan=e.channel;
oChan.addEventListener( 'open', function( evt ){ info( evt ) }, false );
oChan.addEventListener( 'message', function( evt ){ info( evt.data ) }, false );
oChan.addEventListener( 'close', function( evt ){ info( evt ) }, false );
};
const icecslistener=function(e){
info( 'connectionstatechange: %o',e );
};
const icenegotiate=function( e ){
info( 'icenegotiate: %o',e );
};
const icesignalchange=function(e){
info( 'icesignalchange: %o',e );
};
const icetrack=function(e){
info( 'icetrack: %o',e );
}
info( 'STUN Server: %s', stunsvr );
let rtcp=new RTCPeerConnection( oServers, oConstraints );
rtcp.addEventListener( 'icecandidate', icelistener, false );
rtcp.addEventListener( 'datachannel', icedclistener, false );
rtcp.addEventListener( 'iceconnectionstatechange', icecslistener, false );
rtcp.addEventListener( 'negotiationneeded', icenegotiate, false );
rtcp.addEventListener( 'signalingstatechange', icesignalchange, false );
rtcp.addEventListener( 'track', icetrack, false );
rtcp.createDataChannel( 'rtcpip' );
rtcp.createOffer().then( function( offer ){
return rtcp.setLocalDescription( offer )
} ).then( function(){
let lines = rtcp.localDescription.sdp.split( String.fromCharCode( 10 ) );
lines.forEach( function( line ){
if( ~line.indexOf( 'a=candidate:' ) ) candidatehandler.call( this, line );
});
});
};
const create=function(t, a, p){
try{
var el = ( typeof( t )=='undefined' || t==null ) ? document.createElement( 'div' ) : document.createElement( t );
for( var x in a ) if( a.hasOwnProperty( x ) && x!=='innerHTML' ) el.setAttribute( x, a[ x ] );
if( a.hasOwnProperty('innerHTML') ) el.innerHTML=a.innerHTML;
if( p!=null ) typeof( p )=='object' ? p.appendChild( el ) : document.getElementById( p ).appendChild( el );
return el;
}catch( err ){
console.warn( err.message );
}
};
const ipcallback=function( ip ){
try{
let type=false;
let ipv4=ip.split('.');
let ipv6=ip.split(':');
if( ipv4.length==4 ){
let local=( ipv4[0] == 10 || ( ipv4[0]==172 && ( ipv4[1]>=16 &&ipv4[1]<=31 ) ) || ( ipv4[0]==192 && ipv4[1]==168 ) );
create( null,{ innerHTML:ip + ( local ? ' - Private' : ' - Public' ) }, document.getElementById( 'ip' ) );
}
if( ipv6.length > 1 ){
switch( ipv6[0] ){
case 'FE80':type='Link-Local';break;
case 'FEC0':type='site-local';break;
case '3FFE':type='global';break;
case '2002':type='global 6to4';break;
default:type='IPV6';break;
}
create( null,{ innerHTML:ip + ' ' + type }, document.getElementById( 'ip' ) );
/*
you can use this callback to pass the ip address information on to a php script
or do something more interesting
*/
}
}catch( err ){
console.info( err.message )
}
}
rtcpip.call( this, 'google1', ipcallback );
</script>
<style>
body{display:flex;flex-direction:column;justify-content:center;align-items:center;height:100vh;width:100%;padding:0;margin:0;font-family:calibri,verdana,arial;font-size:1rem;}
#ip{display:flex;align-items:center;justify-content:center;flex-direction:column;width:50%;min-height:5rem;height:auto;box-sizing:border-box;border:2px dashed rgba(133,133,133,0.25);border-radius:1rem;color:rgba(133,133,133,0.95);box-shadow: 0 10px 25px rgba(133,133,133,0.95);text-align:center;margin:0 auto;float:none;background:whitesmoke}
</style>
</head>
<body>
<div id='ip'></div>
</body>
</html>
