PHP Manual
Prev | Appendix L. List of Reserved Words | Next

# Predefined Variables

Since PHP 4.1.0, the preferred method for retrieving external variables is with the superglobals mentioned below. Before this time, people relied on either register_globals or the long predefined PHP arrays (`$HTTP_*_VARS`). As of PHP 5.0.0, the long PHP predefined variable arrays may be disabled with the register_long_arrays directive.

## Server variables: `$_SERVER`

> Note: Introduced in 4.1.0. In earlier versions, use `$HTTP_SERVER_VARS`.

`$_SERVER` is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server. There is no guarantee that every web server will provide any of these; servers may omit some, or provide others not listed here. That said, a large number of these variables are accounted for in the CGI 1.1 specification, so you should be able to expect those.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_SERVER; to access it within functions or methods, as you do with `$HTTP_SERVER_VARS`.

`$HTTP_SERVER_VARS` contains the same initial information, but is not a superglobal. (Note that `$HTTP_SERVER_VARS` and `$_SERVER` are different variables and that PHP handles them as such)

If the register_globals directive is set, then these variables will also be made available in the global scope of the script; i.e., separate from the `$_SERVER` and `$HTTP_SERVER_VARS` arrays. For related information, see the security chapter titled Using Register Globals. These individual globals are not superglobals.

You may or may not find any of the following elements in $_SERVER. Note that few, if any, of these will be available (or indeed have any meaning) if running PHP on the command line.

'`PHP_SELF`'

  The filename of the currently executing script, relative to the document root. For instance, `$_SERVER['PHP_SELF']` in a script at the address `http://example.com/test.php/foo.bar` would be `/test.php/foo.bar`. The __FILE__ constant contains the full path and filename of the current (i.e. included) file.

  If PHP is running as a command-line processor this variable contains the script name since PHP 4.3.0. Previously it was not available.

'`argv`'

  Array of arguments passed to the script. When the script is run on the command line, this gives C-style access to the command line parameters. When called via the GET method, this will contain the query string.

'`argc`'

  Contains the number of command line parameters passed to the script (if run on the command line).

'`GATEWAY_INTERFACE`'

  What revision of the CGI specification the server is using; i.e. '`CGI/1.1`'.

'`SERVER_ADDR`'

  The IP address of the server under which the current script is executing.

'`SERVER_NAME`'

  The name of the server host under which the current script is executing. If the script is running on a virtual host, this will be the value defined for that virtual host.

'`SERVER_SOFTWARE`'

  Server identification string, given in the headers when responding to requests.

'`SERVER_PROTOCOL`'

  Name and revision of the information protocol via which the page was requested; i.e. '`HTTP/1.0`';

'`REQUEST_METHOD`'

  Which request method was used to access the page; i.e. '`GET`', '`HEAD`', '`POST`', '`PUT`'.

  > Note: PHP script is terminated after sending headers (it means after producing any output without output buffering) if the request method was `HEAD`.

'`REQUEST_TIME`'

  The timestamp of the start of the request. Available since PHP 5.1.0.

'`QUERY_STRING`'

  The query string, if any, via which the page was accessed.

'`DOCUMENT_ROOT`'

  The document root directory under which the current script is executing, as defined in the server's configuration file.

'`HTTP_ACCEPT`'

  Contents of the `Accept:` header from the current request, if there is one.

'`HTTP_ACCEPT_CHARSET`'

  Contents of the `Accept-Charset:` header from the current request, if there is one. Example: '`iso-8859-1,*,utf-8`'.

'`HTTP_ACCEPT_ENCODING`'

  Contents of the `Accept-Encoding:` header from the current request, if there is one. Example: '`gzip`'.

'`HTTP_ACCEPT_LANGUAGE`'

  Contents of the `Accept-Language:` header from the current request, if there is one. Example: '`en`'.

'`HTTP_CONNECTION`'

  Contents of the `Connection:` header from the current request, if there is one. Example: '`Keep-Alive`'.

'`HTTP_HOST`'

  Contents of the `Host:` header from the current request, if there is one.

'`HTTP_REFERER`'

  The address of the page (if any) which referred the user agent to the current page. This is set by the user agent. Not all user agents will set this, and some provide the ability to modify `HTTP_REFERER` as a feature. In short, it cannot really be trusted.

'`HTTP_USER_AGENT`'

  Contents of the `User-Agent:` header from the current request, if there is one. This is a string denoting the user agent being which is accessing the page. A typical example is: `Mozilla/4.5 [en] (X11; U; Linux 2.2.9 i586)`. Among other things, you can use this value with get_browser() to tailor your page's output to the capabilities of the user agent.

'`HTTPS`'

  Set to a non-empty value if the script was queried through the HTTPS protocol.

  Note that when using ISAPI with IIS, the value will be `off` if the request was not made through the HTTPS protocol.

'`REMOTE_ADDR`'

  The IP address from which the user is viewing the current page.

'`REMOTE_HOST`'

  The Host name from which the user is viewing the current page. The reverse dns lookup is based off the `REMOTE_ADDR` of the user.

  > Note: Your web server must be configured to create this variable. For example in Apache you'll need `HostnameLookups On` inside `httpd.conf` for it to exist. See also gethostbyaddr().

'`REMOTE_PORT`'

  The port being used on the user's machine to communicate with the web server.

'`SCRIPT_FILENAME`'

  The absolute pathname of the currently executing script.

  > Note: If a script is executed with the CLI, as a relative path, such as `file.php` or `../file.php`, `$_SERVER['SCRIPT_FILENAME']` will contain the relative path specified by the user.

'`SERVER_ADMIN`'

  The value given to the SERVER_ADMIN (for Apache) directive in the web server configuration file. If the script is running on a virtual host, this will be the value defined for that virtual host.

'`SERVER_PORT`'

  The port on the server machine being used by the web server for communication. For default setups, this will be '`80`'; using SSL, for instance, will change this to whatever your defined secure HTTP port is.

'`SERVER_SIGNATURE`'

  String containing the server version and virtual host name which are added to server-generated pages, if enabled.

'`PATH_TRANSLATED`'

  Filesystem- (not document root-) based path to the current script, after the server has done any virtual-to-real mapping.

  > Note: As of PHP 4.3.2, `PATH_TRANSLATED` is no longer set implicitly under the Apache 2 SAPI in contrast to the situation in Apache 1, where it's set to the same value as the `SCRIPT_FILENAME` server variable when it's not populated by Apache. This change was made to comply with the CGI specification that `PATH_TRANSLATED` should only exist if `PATH_INFO` is defined.

  > Apache 2 users may use `AcceptPathInfo = On` inside `httpd.conf` to define `PATH_INFO`.

'`SCRIPT_NAME`'

  Contains the current script's path. This is useful for pages which need to point to themselves. The __FILE__ constant contains the full path and filename of the current (i.e. included) file.

'`REQUEST_URI`'

  The URI which was given in order to access this page; for instance, '`/index.html`'.

'`PHP_AUTH_DIGEST`'

  When running under Apache as module doing Digest HTTP authentication this variable is set to the 'Authorization' header sent by the client (which you should then use to make the appropriate validation).

'`PHP_AUTH_USER`'

  When running under Apache or IIS (ISAPI on PHP 5) as module doing HTTP authentication this variable is set to the username provided by the user.

'`PHP_AUTH_PW`'

  When running under Apache or IIS (ISAPI on PHP 5) as module doing HTTP authentication this variable is set to the password provided by the user.

'`AUTH_TYPE`'

  When running under Apache as module doing HTTP authenticated this variable is set to the authentication type.

## Environment variables: `$_ENV`

> Note: Introduced in 4.1.0. In earlier versions, use `$HTTP_ENV_VARS`.

These variables are imported into PHP's global namespace from the environment under which the PHP parser is running. Many are provided by the shell under which PHP is running and different systems are likely running different kinds of shells, a definitive list is impossible. Please see your shell's documentation for a list of defined environment variables.

Other environment variables include the CGI variables, placed there regardless of whether PHP is running as a server module or CGI processor.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_ENV; to access it within functions or methods, as you do with `$HTTP_ENV_VARS`.

`$HTTP_ENV_VARS` contains the same initial information, but is not a superglobal. (Note that `$HTTP_ENV_VARS` and `$_ENV` are different variables and that PHP handles them as such)

If the register_globals directive is set, then these variables will also be made available in the global scope of the script; i.e., separate from the `$_ENV` and `$HTTP_ENV_VARS` arrays. For related information, see the security chapter titled Using Register Globals. These individual globals are not superglobals.

## HTTP Cookies: `$_COOKIE`

> Note: Introduced in 4.1.0. In earlier versions, use `$HTTP_COOKIE_VARS`.

An associative array of variables passed to the current script via HTTP cookies. Automatically global in any scope.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_COOKIE; to access it within functions or methods, as you do with `$HTTP_COOKIE_VARS`.

`$HTTP_COOKIE_VARS` contains the same initial information, but is not a superglobal. (Note that `$HTTP_COOKIE_VARS` and `$_COOKIE` are different variables and that PHP handles them as such)

If the register_globals directive is set, then these variables will also be made available in the global scope of the script; i.e., separate from the `$_COOKIE` and `$HTTP_COOKIE_VARS` arrays. For related information, see the security chapter titled Using Register Globals. These individual globals are not superglobals.

## HTTP GET variables: `$_GET`

> Note: Introduced in 4.1.0. In earlier versions, use `$HTTP_GET_VARS`.

An associative array of variables passed to the current script via the HTTP GET method. Automatically global in any scope.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_GET; to access it within functions or methods, as you do with `$HTTP_GET_VARS`.

`$HTTP_GET_VARS` contains the same initial information, but is not a superglobal. (Note that `$HTTP_GET_VARS` and `$_GET` are different variables and that PHP handles them as such)

If the register_globals directive is set, then these variables will also be made available in the global scope of the script; i.e., separate from the `$_GET` and `$HTTP_GET_VARS` arrays. For related information, see the security chapter titled Using Register Globals. These individual globals are not superglobals.

## HTTP POST variables: `$_POST`

> Note: Introduced in 4.1.0. In earlier versions, use `$HTTP_POST_VARS`.

An associative array of variables passed to the current script via the HTTP POST method. Automatically global in any scope.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_POST; to access it within functions or methods, as you do with `$HTTP_POST_VARS`.

`$HTTP_POST_VARS` contains the same initial information, but is not a superglobal. (Note that `$HTTP_POST_VARS` and `$_POST` are different variables and that PHP handles them as such)

If the register_globals directive is set, then these variables will also be made available in the global scope of the script; i.e., separate from the `$_POST` and `$HTTP_POST_VARS` arrays. For related information, see the security chapter titled Using Register Globals. These individual globals are not superglobals.

## HTTP File upload variables: `$_FILES`

> Note: Introduced in 4.1.0. In earlier versions, use `$HTTP_POST_FILES`.

An associative array of items uploaded to the current script via the HTTP POST method. Automatically global in any scope.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_FILES; to access it within functions or methods, as you do with `$HTTP_POST_FILES`.

`$HTTP_POST_FILES` contains the same information, but is not a superglobal. (Note that `$HTTP_POST_FILES` and `$_FILES` are different variables and that PHP handles them as such)

If the register_globals directive is set, then these variables will also be made available in the global scope of the script; i.e., separate from the `$_FILES` and `$HTTP_POST_FILES` arrays. For related information, see the security chapter titled Using Register Globals. These individual globals are not superglobals.

## Request variables: `$_REQUEST`

> Note: Introduced in 4.1.0. There is no equivalent array in earlier versions.

> Note: Prior to PHP 4.3.0, `$_FILES` information was also included in `$_REQUEST`.

An associative array consisting of the contents of `$_GET`, `$_POST`, and `$_COOKIE`.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_REQUEST; to access it within functions or methods.

If the register_globals directive is set, then these variables will also be made available in the global scope of the script; i.e., separate from the `$_REQUEST` array. For related information, see the security chapter titled Using Register Globals. These individual globals are not superglobals.

## Session variables: `$_SESSION`

> Note: Introduced in 4.1.0. In earlier versions, use `$HTTP_SESSION_VARS`.

An associative array containing session variables available to the current script. See the Session functions documentation for more information on how this is used.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $_SESSION; to access it within functions or methods, as you do with `$HTTP_SESSION_VARS`.

`$HTTP_SESSION_VARS` contains the same information, but is not a superglobal. (Note that `$HTTP_SESSION_VARS` and `$_SESSION` are different variables and that PHP handles them as such)

If the register_globals directive is set, then these variables will also be made available in the global scope of the script; i.e., separate from the `$_SESSION` and `$HTTP_SESSION_VARS` arrays. For related information, see the security chapter titled Using Register Globals. These individual globals are not superglobals.

## Global variables: `$GLOBALS`

> Note: `$GLOBALS` has been available since PHP 3.0.0.

An associative array containing references to all variables which are currently defined in the global scope of the script. The variable names are the keys of the array.

This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. You don't need to do a global $GLOBALS; to access it within functions or methods.

## The previous error message: `$php_errormsg`

`$php_errormsg` is a variable containing the text of the last error message generated by PHP. This variable will only be available within the scope in which the error occurred, and only if the track_errors configuration option is turned on (it defaults to off).

Prev | Home | Next
List of Reserved Words | Up | Predefined Classes