What PHP functions can be used to display a visitor's IP address, operating system, and browser?

To display a visitor's IP address, operating system, and browser in PHP, you can use the following functions: 1. `$_SERVER['REMOTE_ADDR']` to get the visitor's IP address. 2. `$_SERVER['HTTP_USER_AGENT']` to get the visitor's browser information. 3. `get_browser()` function to get detailed browser information, including the operating system. Here is a PHP code snippet that demonstrates how to display a visitor's IP address, operating system, and browser:

$ip_address = $_SERVER['REMOTE_ADDR'];
$browser = $_SERVER['HTTP_USER_AGENT'];
$browser_info = get_browser(null, true);

echo "Visitor's IP Address: " . $ip_address . "<br>";
echo "Browser: " . $browser . "<br>";
echo "Operating System: " . $browser_info['platform'] . "<br>";