| There's a special superglobal array, $_SERVER, that contains a great deal of information about what's going on with your web application. For example, $_SERVER['PHP_SELF'] holds the name of the current script, $_SERVER['REQUEST_METHOD'] holds the request method that was used ("GET", "POST", and so on), $_SERVER['HTTP_USER_AGENT'] holds the type of the user's browser, and so on. You can see a sampling of the most useful server variables available in $_SERVER in Table 6-1. Table 6-1. The General Server VariablesServer variable | Description |
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'AUTH_TYPE' | When running under Apache as module doing HTTP authentication, this variable holds the authentication type. | 'DOCUMENT_ROOT' | The document root directory under which the script is executing, as defined in the server's configuration file. | 'GATEWAY_INTERFACE' | The revision of the CGI specification that the server is using, such as 'CGI/1.1'. | 'PATH_TRANSLATED' | File systembased path to the current script. | 'PHP_AUTH_PW' | When running under Apache as module doing HTTP authentication, this variable holds the password provided by the user. | 'PHP_AUTH_USER' | When running under Apache as module doing HTTP authentication, this variable holds the username provided by the user. | 'PHP_SELF' | The filename of the currently executing script, relative to the document root. | 'QUERY_STRING' | The query string, if any, with which the page was accessed. | '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. | 'REMOTE_PORT' | The port being used on the user's machine to communicate with the web server. | 'REQUEST_METHOD' | Specifies which request method was used to access the page; such as 'GET', 'HEAD', 'POST', 'PUT'. | 'REQUEST_URI' | The URI that was given in order to access this page, such as '/index.html'. | 'SCRIPT_FILENAME' | The absolute pathname of the currently executing script. | 'SCRIPT_NAME' | Contains the current script's path. This is useful for pages that need to point to themselves. | 'SERVER_ADMIN' | The value given to the SERVER_ADMIN directive (for Apache) in the web server configuration file. | 'SERVER_NAME' | The name of the server host under which the script is executing. | 'SERVER_PORT' | The port on the server machine being used by the web server for communication. By default setups, this is '80'. | 'SERVER_PROTOCOL' | Name and revision of the information protocol through which the page was requested; such as 'HTTP/1.0'. | 'SERVER_SIGNATURE' | String containing the server version and virtual host name, which are added to server-generated pages. | 'SERVER_SOFTWARE' | The server identification string. |
NOTE The $HTTP_SERVER_VARS array contains the same information as shown in Tables 6-1 and 6-2 but is not a superglobal. Table 6-2. The HTTP Server VariablesHTTP variable | Description |
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'HTTP_ACCEPT' | Text in the Accept: header from the current request, if there is one. | 'HTTP_ACCEPT_CHARSET' | Text in the Accept-Charset: header from the current request, if there is one, such as: '*, utf-8'. | 'HTTP_ACCEPT_ENCODING' | Text in the Accept-Encoding: header from the current request, if there is one, such as: 'zip'. | 'HTTP_ACCEPT_LANGUAGE' | Text in the Accept-Language: header from the current request, if there is one, such as 'en' for English. | 'HTTP_CONNECTION' | Text in the Connection: header from the current request, if there is one, such as: 'Keep-Alive'. | 'HTTP_HOST' | Text in the Host: header from the current request, if there is one. | 'HTTP_REFERER' | The address of the page (if any) that referred the user agent to the current page. The browser sets this. | 'HTTP_USER_AGENT' | Text in the User-Agent: header from the current request, if there is one. This is a string denoting the browser that is accessing the page. |
These server variables are great because they give you a little more informationsuch as the name of the script that's running in this example, phpidentifier.php: <HTML> <HEAD><TITLE>The Self Identifier Script</TITLE></HEAD> <BODY> <H1>The Self Identifier Script</H1> <?php echo "Welcome to ", $_SERVER["PHP_SELF"]; ?> </BODY> </HTML>
Here's what you see when you run this script: Welcome to /phpindentifier.php
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