Today I’ll be showing you how to grab somebodies IP address when they visit a page.

The variable to use is $_SERVER['REMOTE_ADDR'] - It’s that simple. You can use it 
for just about anything, here are a few examples.

Printing the Users IP Address:
<?php 
print ($_SERVER['REMOTE_ADDR'], "I'm Watching You!"); 
?> 






Printing it to a File:

<?php 
$ip = $_SERVER['REMOTE_ADDR']; 
$handle = fopen('ipaddresses.txt'', 'a+); 
fwrite($handle, $ip); fwrite($handle, "\n"); 
fclose($handle); 
?>

All you have to do, is to make a text file and insert any of these codes or one of your 
own and save it as anythingyouwant.php 
Then upload it to your website and it'll do the trick :P

The Possibilities for what you can use this to are endless. 

Good luck :D