$_SERVER Since: PHP 4（2000）

A superglobal variable that provides information about the web server and HTTP request details. It is used as the foundation for server-side processing such as detecting the request method and building redirect URLs.

Syntax

// Gets the request method.
$_SERVER['REQUEST_METHOD'];

// Gets the hostname.
$_SERVER['HTTP_HOST'];

// Gets the request URI.
$_SERVER['REQUEST_URI'];

// Gets the absolute file path of the script.
$_SERVER['SCRIPT_FILENAME'];

Variable List

Key	Description
REQUEST_METHOD	Returns the HTTP method used for the request. Possible values include `GET`, `POST`, `PUT`, and `DELETE`.
HTTP_HOST	Returns the hostname of the request destination. Contains the value of the Host header.
REQUEST_URI	Returns the URI of the request. Contains the full path including the query string.
QUERY_STRING	Returns the query string portion of the URL after the `?`.
SCRIPT_NAME	Returns the path of the currently executing script.
SCRIPT_FILENAME	Returns the absolute file path of the currently executing script.
DOCUMENT_ROOT	Returns the document root path of the web server.
REMOTE_ADDR	Returns the IP address of the client. When accessed through a proxy, this may be the IP of the intermediate server.
HTTP_USER_AGENT	Returns the browser's User-Agent string.
HTTP_REFERER	Returns the URL of the referring page. This may not always be present, as some browsers do not send it.
HTTPS	Set to `on` for HTTPS connections. Undefined for HTTP connections.
SERVER_PORT	Returns the port number of the server. Typically `80` or `443`.
CONTENT_TYPE	Returns the value of the Content-Type header from the request.

Sample Code

<?php
// Check the request method.
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
	echo "Received a POST request.";
} else {
	echo "This is a GET request."; // Output when accessed via a browser.
}

// Build the current URL.
$scheme = isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? 'https' : 'http';
$host = $_SERVER['HTTP_HOST'];
$uri = $_SERVER['REQUEST_URI'];
$currentUrl = $scheme . '://' . $host . $uri;
echo $currentUrl; // Outputs something like: 'https://example.com/page.php?id=1'

// Get the client's IP address.
$ip = $_SERVER['REMOTE_ADDR'];
echo "Client IP: " . $ip; // Outputs something like: 'Client IP: 192.168.1.100'

// Get the User-Agent string.
$ua = $_SERVER['HTTP_USER_AGENT'] ?? '';
echo "Browser: " . htmlspecialchars($ua);

// Check the referrer. Use isset() since it may not be set.
if (isset($_SERVER['HTTP_REFERER'])) {
	echo "Referrer: " . htmlspecialchars($_SERVER['HTTP_REFERER']);
} else {
	echo "No referrer information available.";
}

// Check the script path information.
echo $_SERVER['SCRIPT_NAME']; // Outputs something like: '/index.php'
echo $_SERVER['DOCUMENT_ROOT']; // Outputs something like: '/var/www/html'

// Get the query string.
// URL: page.php?category=php&page=2
echo $_SERVER['QUERY_STRING']; // Outputs: 'category=php&page=2'

Notes

$_SERVER is a superglobal variable that holds information about the web server and HTTP request. Some values in $_SERVER are taken from HTTP headers sent by the client and may contain untrusted data. Always escape them with htmlspecialchars() before outputting to HTML.

In particular, HTTP_HOST, HTTP_REFERER, HTTP_USER_AGENT, and REQUEST_URI are header values that the client can set freely. When using these values in security-sensitive operations, validate them against a whitelist.

Use $_GET / $_POST for retrieving request data, and header() for sending HTTP headers.

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PHP Dictionary

$_SERVER Since: PHP 4（2000）

Syntax

Variable List

Sample Code

Notes