How to Retrieve the Referrer URL in PHP
When tracking user behavior on your website, it's often desirable to know where they came from. PHP provides a convenient way to access the referrer URL through the $_SERVER['HTTP_REFERER'] variable.
However, it's essential to note that this variable may not always contain the expected value. For instance, if a user comes directly to your site by typing in the URL or using a bookmark, $_SERVER['HTTP_REFERER'] will be empty.
Additional Considerations
If you're using the $_SERVER['HTTP_REFERER'] variable and finding that it's consistently empty, consider the following possibilities:
- The user may have disabled the option to send referrer information in their browser settings.
- The user may have used a script or bot to access your site, which generally does not provide referrer information.
- You may have accidentally omitted the leading underscores from $_SERVER['HTTP_REFERER'].
Here's a more comprehensive list of the variables contained in the $_SERVER array:
- DOCUMENT_ROOT: The root folder of your webserver.
- GATEWAY_INTERFACE: The version of the CGI.
- HTTP_ACCEPT: The types of content that the client can accept.
- HTTP_ACCEPT_ENCODING: The encoding that the client can accept.
- HTTP_ACCEPT_LANGUAGE: The language that the client can accept.
- HTTP_CACHE_CONTROL: Controls the caching of the page.
- HTTP_CONNECTION: The connection type used to access the page.
- HTTP_COOKIE: The cookies sent by the client.
- HTTP_HOST: The hostname of the server.
- HTTP_USER_AGENT: The user agent of the client.
- PATH: The search path for scripts.
- QUERY_STRING: The query string sent to the script.
- REDIRECT_STATUS: The status code of the redirect performed by the server.
- REMOTE_ADDR: The IP address of the client.
- REMOTE_PORT: The port number used by the client.
- REQUEST_METHOD: The method used to access the page (GET, POST, etc.).
- REQUEST_URI: The path and query string of the requested page.
- SCRIPT_FILENAME: The absolute path to the script being executed.
- SCRIPT_NAME: The path to the script being executed.
- SERVER_ADDR: The IP address of the server.
- SERVER_ADMIN: The email address of the server administrator.
- SERVER_NAME: The hostname of the server.
- SERVER_PORT: The port number used by the server.
- SERVER_PROTOCOL: The protocol used by the server (HTTP/1.1, HTTP/1.0).
- SERVER_SIGNATURE: The signature of the server (Apache, IIS, etc.).
- SERVER_SOFTWARE: The software used by the server (Apache, IIS, etc.).
- UNIQUE_ID: A unique session identifier.
- PHP_SELF: The name of the current script.
- REQUEST_TIME: The timestamp when the request was made.
- argv: An array of command-line arguments.
- argc: The number of command-line arguments.
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