$_SERVER is a superglobal in PHP. It holds information regarding HTTP headers, path and script location, etc.
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$_SERVER is an associative array and it holds all the server and execution environment related information.
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Most of the entries in this associative array are populated by the web server. The entries may change from one web server to other, as servers may omit some, or provide others.
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For a PHP script running on the command line, most of these entries will not be available or have any meaning.
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PHP will also create additional elements with values from request headers. These entries will be named “HTTP_” followed by the header name, capitalized and with underscores instead of hyphens.
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For example, the “Accept-Language” header would be available as $_SERVER[”HTTP_ACCEPT_LANGUAGE”].
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PHP versions prior to 5.4.0 had $HTTP_SERVER_VARS which contained the same information but it has now been removed.
The following table lists some of the important server variables of the $_SERVER array followed by the description of their values.
| Sr.No | Server Variables & Description |
|---|---|
| 1 |
PHP_SELF Stores filename of currently executing script. |
| 2 |
SERVER_ADDR This property of array returns the IP address of the server under which the current script is executing. |
| 3 |
SERVER_NAME Name of server host under which the current script is executing. In case of a server running locally, localhost is returned. |
| 4 |
QUERY_STRING A query string is the string of key value pairs separated by the “&” symbol and appended to the URL after the “?” symbol. For example, http://localhost/testscript?name=xyz&age=20 URL returns trailing query string |
| 5 |
REQUEST_METHOD HTTP request method used for accessing a URL, such as POST, GET, POST, PUT or DELETE. In the above query string example, a URL attached to query string with the “?” symbol requests the page with GET method |
| 6 |
DOCUMENT_ROOT Returns the name of the directory on the server that is configured as the document root. On XAMPP apache server, it returns htdocs as the name of document root c:/xampp/htdocs |
| 7 |
REMOTE_ADDR IP address of the machine from where the user is viewing the current page. |
| 8 |
SERVER_PORT Port number on which the web server is listening to the incoming request. Default is 80 |
Example
The following script invoked from document root of XAMPP server lists all the server variables −
<?php foreach ($_SERVER as $k=>$v) echo $k . "=>" . $v . "n"; ?>
It will produce the following output −
MIBDIRS=>C:/xampp/php/extras/mibs MYSQL_HOME=>xamppmysqlbin OPENSSL_CONF=>C:/xampp/apache/bin/openssl.cnf PHP_PEAR_SYSCONF_DIR=>xamppphp PHPRC=>xamppphp TMP=>xampptmp HTTP_HOST=>localhost HTTP_CONNECTION=>keep-alive HTTP_SEC_CH_UA=>"Chromium";v="116", "Not) A;Brand";v="24", "Google Chrome";v="116" HTTP_SEC_CH_UA_MOBILE=>?0 HTTP_SEC_CH_UA_PLATFORM=>"Windows" HTTP_DNT=>1 HTTP_UPGRADE_INSECURE_REQUESTS=>1 HTTP_USER_AGENT=>Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36 HTTP_ACCEPT=>text/html,application/xhtml+xml,application/xml; q=0.9,image/avif,image/webp,image/apng,*/*; q=0.8,application/signed-exchange;v=b3;q=0.7 HTTP_SEC_FETCH_SITE=>none HTTP_SEC_FETCH_MODE=>navigate HTTP_SEC_FETCH_USER=>?1 HTTP_SEC_FETCH_DEST=>document HTTP_ACCEPT_ENCODING=>gzip, deflate, br HTTP_ACCEPT_LANGUAGE=>en-US,en;q=0.9,mr;q=0.8 PATH=>C:Python311Scripts; C:Python311;C:WINDOWSsystem32; C:WINDOWS;C:WINDOWSSystem32Wbem; C:WINDOWSSystem32WindowsPowerShellv1.0; C:WINDOWSSystem32OpenSSH;C:xamppphp; C:UsersuserAppDataLocalMicrosoftWindowsApps; C:VSCodeMicrosoft VS Codebin SystemRoot=>C:WINDOWS COMSPEC=>C:WINDOWSsystem32cmd.exe PATHEXT=>.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC;.PY;.PYW WINDIR=>C:WINDOWS SERVER_SIGNATURE=> Apache/2.4.56 (Win64) OpenSSL/1.1.1t PHP/8.0.28 Server at localhost Port 80 SERVER_SOFTWARE=>Apache/2.4.56 (Win64) OpenSSL/1.1.1t PHP/8.0.28 SERVER_NAME=>localhost SERVER_ADDR=>::1 SERVER_PORT=>80 REMOTE_ADDR=>::1 DOCUMENT_ROOT=>C:/xampp/htdocs REQUEST_SCHEME=>http CONTEXT_PREFIX=> CONTEXT_DOCUMENT_ROOT=>C:/xampp/htdocs SERVER_ADMIN=>postmaster@localhost SCRIPT_FILENAME=>C:/xampp/htdocs/hello.php REMOTE_PORT=>54148 GATEWAY_INTERFACE=>CGI/1.1 SERVER_PROTOCOL=>HTTP/1.1 REQUEST_METHOD=>GET QUERY_STRING=> REQUEST_URI=>/hello.php SCRIPT_NAME=>/hello.php PHP_SELF=>/hello.php REQUEST_TIME_FLOAT=>1694802456.9816 REQUEST_TIME=>1694802456