Getting the visitor IP address in PHP

<?php
$ip = $_SERVER['REMOTE_ADDR'] ?? '';

if (filter_var($ip, FILTER_VALIDATE_IP)) {
    echo 'IP address = ' . htmlspecialchars($ip, ENT_QUOTES, 'UTF-8');
} else {
    echo 'IP address is not available.';
}
?>

PHP can read the address associated with the current HTTP connection. IP information is useful for logging, troubleshooting, rate limiting and security auditing, but an IP address should not be treated as a permanent identity for a person.

What is my IP address?

The basic form is:

<?php
$ip = $_SERVER['REMOTE_ADDR'] ?? '';
echo 'IP address = ' . $ip;
?>

The server currently reports: 216.73.217.99

Proxy and forwarded-address headers

Headers such as HTTP_X_FORWARDED_FOR can be supplied or altered by clients. Do not automatically treat them as the visitor's real IP address. Only parse a forwarded header when your application is behind a trusted proxy that you configured.

<?php
$connectionIp = $_SERVER['REMOTE_ADDR'] ?? '';
$forwardedFor = $_SERVER['HTTP_X_FORWARDED_FOR'] ?? null;

// Trust $forwardedFor only when REMOTE_ADDR is one of your known proxies.
?>

Other server variables

$_SERVER is an associative array containing request and server information. For example, the server name can be read like this:

<?php
$serverName = $_SERVER['SERVER_NAME'] ?? 'unknown';
echo htmlspecialchars($serverName, ENT_QUOTES, 'UTF-8');
?>

To inspect all available entries, use foreach. The old each() function was removed from PHP and should not be used.

<?php
foreach ($_SERVER as $key => $value) {
    if (is_scalar($value)) {
        echo htmlspecialchars((string) $key, ENT_QUOTES, 'UTF-8')
           . ' -> '
           . htmlspecialchars((string) $value, ENT_QUOTES, 'UTF-8')
           . '<br>';
    }
}
?>

Dynamic and static IP addresses

Many internet connections receive an address dynamically from the ISP, so a visitor's public IP can change. A static address remains assigned to the same connection and is useful for services that require a predictable network endpoint.

Binary storage that supports IPv4 and IPv6

inet_pton() converts a valid address to packed binary form, which can be stored in a binary column and later converted back with inet_ntop().

<?php
$packed = inet_pton($ip);
if ($packed !== false) {
    // Store $packed in an appropriately sized binary column.
}
?>

DNS and host names

DNS maps domain names to network addresses. PHP can resolve host names with functions such as gethostbyname(), while checkdnsrr() can test DNS record types.

Storing IP addresses

If an application stores visitor addresses, use a field that supports both IPv4 and IPv6. Store only what your application actually needs.

• Collecting the visitor referrer
• Resolving a domain with gethostbyname()
• Host-name lookup demo
• Logging visitor details
• Checking DNS records
• Checking HTTPS server information

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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