A Sneak Peek into The $_SERVER in PHP

Introduction to the $_SERVER in PHP

$_SERVER in PHP is a superglobal variable. This variable is an associative array that stores the information about the server, path, and script. PHP provides various parameters that can be passed in $_SERVER like $_SERVER['PHP_SELF'], $_SERVER['SERVER_PROTOCOL'], etc. These parameters decide the behavior of the $_SERVER variable.

In this article, you will explore the necessity for the $_SERVER in PHP, along with all of its parameters in detail.

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What Are Superglobals in PHP?

Superglobal variables are pre-defined variables that are used to retrieve information about a request. As the name suggests, you can access these variables from anywhere throughout the script, performing no excessive tasks. This means that the scope of these variables is not bounded by any function or class. 

PHP provides 9 types of superglobal variables. All these superglobal variables are listed below with their brief description:

Uses of $_SERVER in PHP

$_SERVER in PHP is used to store information such as the server information, port number, script path, and so on. The following script illustrates the usage of the variable $_SERVER in PHP:

<?php 

    // display directory name

    echo "The file name is: ";

    echo $_SERVER['PHP_SELF']; 

    echo '<br>'; 

    // display server name

    echo "The server name is: ";

    echo $_SERVER['SERVER_NAME']; 

    echo '<br>'; 

    // display server protocol

    echo "The server protocol is: ";

    echo $_SERVER['SERVER_PROTOCOL']; 

    echo '<br>'; 

    // display server port

    echo "The server port number is: ";

    echo $_SERVER['SERVER_PORT'];

?>

The script mentioned above displays the details of the script file and the host server. The information such as the file directory, server name, server port, and URI can be easily retrieved using the variable $_SERVER in PHP. 

All the arguments that are passed to $_SERVER in PHP can be broadly classified into 6 categories based on their functioning and usage. These categories are as follows:

• Server details: Information about the server like server name, IP address of the server, port number of the server, etc.

• Header details: Header information such as the connection, language accepted by the server, set of characters used, and so on.

• Details of the PHP page request: Details of the page request such as the request method passed (GET or POST), timestamp of the request, and so on.

• Name of the file or path details: This includes information like the URL of the current page, the pathname of the script, etc.

• Remote client details: Details about the client’s machine with which the page is being accessed such as the IP address and the port number of the user’s machine.

• HTTP Authentication Details:  Details about the authenticity of the user, such as username and password entered by the client.

$_SERVER Parameters

The $_SERVER variable contains a list of data, such as path, headers, script locations,  and many more. It is an associative array and has quite a few key-value pairs as well. You can access these elements by simply passing the name of the parameter that you want to access. In this article, you will look into the following parameters in detail.

1. $_SERVER[‘PHP_SELF’]
2. $_SERVER[‘GATEWAY_INTERFACE’]
3. $_SERVER[‘SERVER_ADDR’]
4. $_SERVER[‘SERVER_NAME’]
5. $_SERVER[‘SERVER_SOFTWARE’]
6. $_SERVER[‘SERVER_PROTOCOL’]
7. $_SERVER[‘REQUEST_METHOD’]
8. $_SERVER[‘REQUEST_TIME’]
9. $_SERVER[‘QUERY_STRING’]
10. $_SERVER[‘HTTP_ACCEPT’]
11. $_SERVER[‘HTTP_ACCEPT_CHARSET’]
12. $_SERVER[‘HTTP_HOST’]
13. $_SERVER[‘HTTP_REFERER’]
14. $_SERVER[‘HTTPS’]
15. $_SERVER[‘REMOTE_ADDR’]
16. $_SERVER[’REMOTE_HOST’]
17. $_SERVER[‘REMOTE_PORT’]
18. $_SERVER[‘SCRIPT_FILENAME’]
19. $_SERVER[‘SERVER_ADMIN’]
20. $_SERVER[‘SERVER_PORT’]
21. $_SERVER[‘SERVER_SIGNATURE’]
22. $_SERVER[‘PATH_TRANSLATED’]
23. $_SERVER[‘SCRIPT_NAME’]
24. $_SERVER[‘REQUEST_URI’]

• $_SERVER['PHP_SELF']

$_SERVER[‘PHP-SELF’] is used to get the file name of the script that is currently being executed. When used, this variable returns the file name in two ways: with and without the file name being typed in the URL.

Syntax

<?php

echo $_SERVER['PHP_SELF'];

?>

Example

<?php   

    echo "Example of PHP_SELF<br><br>";

    echo "The file name of the script running currently is: <br><br>";

    // returns the file directory

    echo $_SERVER['PHP_SELF'];

    echo '<br>';

?>

In the above example, the $_SERVER['PHP_SELF'] returns the directory name of the script that is being executed on the server. The complete path is “/test/index.php”, where “test” is the directory name and “index.php” is the file name.

• $_SERVER['GATEWAY_INTERFACE']

$_SERVER[‘GATEWAY_INTERFACE’] is used to get the current version of CGI (Common Gateway Interface) that the server is using. A CGI is an interface that allows the servers to process requests of the clients.

Syntax

<?php

echo $_SERVER['GATEWAY_INTERFACE'];

?>

Example

<?php     

    echo "Example of GATEWAY_INTERFACE<br><br>";

    echo "The version of the Common Gateway Interface is: <br><br>";   

    // returns the CGI version

    echo $_SERVER['GATEWAY_INTERFACE'];

    echo '<br>'; 

?>

In the above example, the $_SERVER['GATEWAY_INTERFACE']  returns CGI/1.1 that is the CGI version under which the script was being executed.  

• $_SERVER['SERVER_ADDR']

$_SERVER['SERVER_ADDR'] is used to get the IP address of the host server. For example, “13.107.6.152/31” is an IP address of a website.

Syntax

<?php

echo $_SERVER['SERVER_ADDR'];

?>

Example

<?php  

    echo "Example of SERVER_ADDR<br><br>";

    echo "The IP address of the host server is: <br><br>";   

    // returns the IP address

    echo $_SERVER['SERVER_ADDR'];

    echo '<br>';

?>

In the above example, the IP address of the localhost server is returned by the $_SERVER['SERVER_ADDR'].

• $_SERVER['SERVER_NAME']

$_SERVER['SERVER_ADDR'] is used to get the name of the host server. For example, “www.microsoft.com”. This variable is useful for those pages that want to point to themselves.

Syntax

<?php

echo $_SERVER['SERVER_NAME'];

?>

Example

<?php 

      echo "Example of SERVER_NAME<br><br>";

    echo "The name of the host server is: <br><br>";

    // returns the server name

    echo $_SERVER['SERVER_NAME'];

    echo '<br>';

?>

In the above example, $_SERVER['SERVER_NAME'] returns the name of the host server. The server is hosted on a local machine to run the above script. So, the script returns “localhost”.

• $_SERVER['SERVER_SOFTWARE']

$_SERVER['SERVER_SOFTWARE'] is used to get the server identification string. The string contains details of the server software.  

Syntax

<?php

echo $_SERVER['SERVER_SOFTWARE'];

?>

Example

<?php    

    echo "Example of SERVER_SOFTWARE<br><br>";

    echo "The server identification string of the host server is: <br><br>";    

    // returns the server software details

    echo $_SERVER['SERVER_SOFTWARE'];

    echo '<br>'; 

?>

In the above example, $_SERVER['SERVER_SOFTWARE'] returns a string containing details of the software used in the localhost server. The server setup is an Apache web server and the host machine is a Windows 64-bit system.

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• $_SERVER['SERVER_PROTOCOL']

$_SERVER['SERVER_PROTOCOL'] is used to get the name and version of the protocol through which it requests the page. A server protocol provides structure in a network for requests between the client and the server. For example, HTTP, HTTPS, TCP/IP all are server protocols.  

Syntax

<?php

echo $_SERVER['SERVER_SOFTWARE'];

?>

Example

<?php 

    echo "Example of SERVER_PROTOCOL<br><br>";

    echo "The protocol and version of the host server is: <br><br>";   

    // returns the protocol

    echo $_SERVER['SERVER_PROTOCOL'];

    echo '<br>';

?>

In the above example, $_SERVER['SERVER_PROTOCOL']  returns the protocol and version of the localhost server. The protocol of the server is HTTP.

• $_SERVER['REQUEST_METHOD']

$_SERVER['REQUEST_METHOD'] is used to know about the request method (for example GET, POST, PUT, etc) that is used to access the page. If the HEAD method is used to access the page, the script will automatically terminate after sending headers.

Syntax

<?php

echo $_SERVER['REQUEST_METHOD'];

?>

Example

<?php     

    echo "Example of REQUEST_METHOD<br><br>";

    echo "The request method is: <br><br>";   

    // returns the request method to access this page

    echo $_SERVER['REQUEST_METHOD'];

    echo '<br>';

?>

In the above example, $_SERVER['REQUEST_METHOD'] is used to display the request method of the page.

• $_SERVER['REQUEST_TIME']

$_SERVER['REQUEST_TIME'] as the name suggests, returns the timestamp of the moment when it started the server. The timestamp is the date and time of a specific moment displayed in the form of characters in a specific format. The $_SERVER['REQUEST_TIME'] in PHP returns a UNIX timestamp.

Syntax

<?php

echo $_SERVER['REQUEST_TIME'];

?>

Example

<?php     

    echo "Example of REQUEST_TIME<br><br>";

    echo "The timestamp of the start of this request is: <br><br>";    

    // returns the UNIX-based timestamp

    echo $_SERVER['REQUEST_TIME'];;

    echo '<br>'; 

?>

In the above example, the timestamp returned is in the UNIX format. When converted to a human-readable format, it will be equivalent to Sunday, May 23, 2021, 12:28:21 PM.

• $_SERVER['QUERY_STRING']

QUERY_STRING is another $_SERVER parameter that returns the query string if it is used to access the page.

Syntax

<?php

echo $_SERVER['QUERY_STRING'];

?>

Example

<?php  

    echo "Example of QUERY_STRING<br><br>";    

    // create 5 links    

    for($i = 1; $i<= 5; $i++) {  

        echo '<a href = "index.php?page=' . $i . '">' . $i . ' </a>';  

    }  

    echo '<br>';

    echo "The executed query is: <br><br>";

    // returns the query of the page

    echo $_SERVER['QUERY_STRING'];

?>   

In the above example, 5 links are created. When any of the links are clicked, it executes a query. The $_SERVER['QUERY_STRING']  returns the executed query (The string after the “?” is the query returned by $_SERVER['QUERY_STRING'] ).

• $_SERVER['HTTP_ACCEPT']

$_SERVER['HTTP_ACCEPT'] is used to get the Accept header (if any) from the current request. The Accept header is an HTTP request type header that is used to educate the server about the type of contents understandable by the client. If you do not pass the Accept header in the request, the server automatically considers all types of content and media understandable by the client.

Syntax

<?php

echo $_SERVER['HTTP_ACCEPT'];

?>

Example

<?php  

   echo "Example of HTTP_ACCEPT<br><br>";

    echo "The details of the accept of HTTP request is:<br><br>";

    // returns the accept header

    echo $_SERVER['HTTP_ACCEPT'];

?>  

In the above example, the  $_SERVER['HTTP_ACCEPT'] returns the details of the Accept header. If the access request does not exist, then it returns nothing in the output.   

• $_SERVER['HTTP_ACCEPT_CHARSET']

$_SERVER['HTTP_ACCEPT_CHARSET'] is used to get the Accept-Charset header (if any) from the current request. This header determines the set of characters that can be used for the form submissions i.e., acceptable for the server response. For example, utf-8, ISO-8859-1 is an HTTP Accept Header.

Syntax

<?php

echo $_SERVER['HTTP_ACCEPT_CHARSET'];

?>

Example

<?php

    echo "Example of HTTP_ACCEPT_CHARSET<br><br>";  

    echo "The detail of the charset accept of HTTP request is:<br><br>";

    // returns the accept header

    echo @$_SERVER['HTTP_ACCEPT_CHARSET'];

?>  

In the above example, the $_SERVER['HTTP_ACCEPT_CHARSET'] returns nothing, as the charset accept header does not exist. 

• $_SERVER['HTTP_HOST']

$_SERVER['HTTP_HOST'] is used to get the host server’s contents i.e., a header from the current request. The HTTP host is nothing but the domain name of the server. For example, in www.microsoft.com  “microsoft.com” is a domain name. The HTTP host header determines the back-end component with which the client wants to interact. 

Syntax

<?php

echo $_SERVER['HTTP_HOST'];

?>

Example

<?php

    echo "Example of HTTP_HOST<br><br>";  

    echo "The name of the host is:<br><br>"; 

    // returns the host name

    echo $_SERVER['HTTP_HOST'];

?>  

In the above example, since the localhost server is used to run the script, the $_SERVER['HTTP_HOST'] returns “localhost” as the name of the host.

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• $_SERVER['HTTP_REFERER']

HTTP_REFERER is a parameter of  $_SERVER in PHP that returns the complete URL of the requested page. However, $_SERVER['HTTP_REFERER'] is not widely used because most web browsers do not support this parameter.

Syntax

<?php

echo $_SERVER['HTTP_REFERER'];

?>

Example

<?php    

    echo "Example of HTTP_REFERER<br><br>"; 

    if (isset($_SERVER['HTTP_REFERER'])) {

        echo "The URL of the previous page is:<br> {$_SERVER['HTTP_REFERER']}<br><br>";

    } else {

        echo "Click the below link to see the working of HTTP_REFERER<br><br>";

    }

?>

<a href="index.php?page=1">Click me!</a> 

In the above example, when you directly access the webpage with the URL “http://localhost/test/index.php”, the $_SERVER['HTTP_REFERER'] returns nothing and it is unset at that moment. But when you click a link to get to another URL, the $_SERVER['HTTP_REFERER'] returns the URL of the previous page.

• $_SERVER['HTTPS']

HTTPS (HyperText Transfer Protocol Secure) is the secured version of the HTTP protocol. $_SERVER[‘HTTPS’] is used to ensure if the script is queried through a secure protocol. If it is, then it assigns a non-empty value.

Syntax

<?php

echo $_SERVER['HTTPS'];

?>

Example

<?php 

    echo "Example of HTTPS<br><br>";

    if(isset($_SERVER['HTTPS'])) {

        echo "{$_SERVER['HTTPS']}<br><br>";

    } else {

        echo "The script is not queried using a secured protocol.<br>";

    }

    echo '<br>';

?>

In the above example, it checks the state of the value return by $_SERVER['HTTPS'] by using the isset() method. Since the protocol used is HTTP which is not secure, the value of $_SERVER['HTTPS'] is not set.  

• $_SERVER['REMOTE_ADDR']

$_SERVER['REMOTE_ADDR'] is used to get the IP address of the client’s machine from which it accesses the page. You can relate this element to the SERVER_ADDR where the element returns the IP address of the host server.

Syntax

<?php

echo $_SERVER['REMOTE_ADDR'];

?>

Example

<?php 

    echo "Example of REMOTE_ADDR<br><br>";

    echo "The IP address of the host machine is: <br><br>";  

    // returns the IP address

    echo $_SERVER['REMOTE_ADDR'];

    echo '<br>'; 

?>

In the above example, the $_SERVER['REMOTE_ADDR'] returns the IP address of the host machine which is running the script.

• $_SERVER['REMOTE_HOST']

REMOTE_HOST is another $_SERVER argument that is used to get the name of the host from where the client accesses and views the current page.

Syntax

<?php

echo $_SERVER['REMOTE_HOST'];

?>

Example

<?php    

    echo "Example of REMOTE_HOST<br><br>";

    echo "The name of the host machine is: <br><br>";   

    // returns the name of the host 

    echo @$_SERVER['REMOTE_HOST'];

    echo '<br>';

?>

In the above example, it displays the name of the host machine which is used to run the script. Since localhost is used on a local machine, it displays the name of that machine i.e. LAPTOP-6971UQ75.

• $_SERVER['REMOTE_PORT']

$_SERVER['REMOTE_PORT'] is just like the other “REMOTE” parameters that deal with the client-side machine rather than the server-side. This parameter returns the port number of the client’s machine that is being used to interact with the server’s machine.

Syntax

<?php

echo $_SERVER['REMOTE_PORT'];

?>

Example

<?php     

    echo "Example of REMOTE_PORT<br><br>";

    echo "The name of the port used is: <br><br>";   

    // returns the port

    echo $_SERVER['REMOTE_PORT'];

    echo '<br>';

?>

In the above example, the port used for the communication with the browser is returned by the $_SERVER['REMOTE_PORT'] as 62254.  

• $_SERVER['SCRIPT_FILENAME']

$_SERVER['SCRIPT_FILENAME'] is used to get the complete pathname of the script file that you currently execute. The returned pathname is the ultimate location where the script file is located or stored.

Syntax

<?php

echo $_SERVER['SCRIPT_FILENAME'];

?>

Example

<?php     

    echo "Example of SCRIPT_FILENAME<br><br>";

    echo "The absolute path of this file is: <br><br>";    

    // returns the complete path

    echo $_SERVER['SCRIPT_FILENAME'];

    echo '<br>'; 

?>

In the above example,  the absolute path of the PHP script file is displayed using the  $_SERVER['SCRIPT_FILENAME']. It returns and displays the complete path including the root directory and the file name.

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• $_SERVER['SERVER_ADMIN']

$_SERVER['SERVER_ADMIN'] is used to return the value assigned to the SERVER_ADMIN for the configuration of the webserver. This value is the email address of the administrator of the webserver. 

Syntax

<?php

echo $_SERVER['SERVER_ADMIN'];

?>

Example

<?php 

    echo "Example of SERVER_ADMIN<br><br>";

    echo "The server admin of this server is: <br><br>";

       // returns the value of SERVER_ADMIN

    echo $_SERVER['SERVER_ADMIN'];

    echo '<br>'; 

?>

In the above example, it returns the ServerAdmin value of the localhost server. Since an Apache setup is being used for the above script, it returns the default value of ServerAdmin, which is “postmaster@localhost”.

• $_SERVER['SERVER_PORT']

$_SERVER['SERVER_PORT'] just like the $_SERVER[‘REMOTE_PORT’] returns the port number. But as the name suggests, it gives the port number of the server machine rather than the client’s machine, which is used by the webserver to communicate to the other end.

Syntax

<?php

echo $_SERVER['SERVER_PORT'];

?>

Example

<?php    

    echo "Example of SERVER_PORT<br><br>";

    echo "The server machine's port is: <br><br>";    

    // returns the server port

    echo $_SERVER['SERVER_PORT'];

    echo '<br>';

?>

In the above example,  it returns port number 80 by the $_SERVER['SERVER_PORT']. Port number 80 is the default port set here by the Apache server, which is used to run the above script.

• $_SERVER['SERVER_SIGNATURE']

$_SERVER['SERVER_SIGNATURE'] is used to return the complete signature of the webserver used to execute the script. The signature is a string containing the version of the server and the name of the host. The value returned is the complete identity of the webserver. 

Syntax

<?php

echo $_SERVER['SERVER_SIGNATURE'];

?>

Example

<?php 

    echo "Example of SERVER_SIGNATURE<br><br>";

    echo "The signature of this server is: <br><br>";    

    // returns the complete signature

    echo $_SERVER['SERVER_SIGNATURE'];

    echo '<br>'; 

?>

In the above example, it displays the string containing the details of the webserver on the web page using the $_SERVER['SERVER_SIGNATURE']. It returns the Apache server’s version and the hostname i.e. “localhost” along with the port number as the signature. 

• $_SERVER['PATH_TRANSLATED']

$_SERVER['PATH_TRANSLATED'] returns the path of the script file based on the filesystem. It returns the path only when you define the PATH_INFO in the configuration file of the server.

Syntax

<?php

echo $_SERVER['PATH_TRANSLATED'];

?>

Example

<?php    

    echo "Example of PATH_TRANSLATED<br><br>";    

    if(isset($_SERVER['PATH_TRANSLATED'])) {

        echo "{$_SERVER['PATH_TRANSLATED']}<br><br>";

    } else {

        echo "The path info has not been defined.<br>";

    }

    echo '<br>'; 

?>

In the above example, it does not define the PATH_INFO, so the $_SERVER['PATH_TRANSLATED'] does return a value. The isset() method is used here to check if the path is set or not.

• $_SERVER['SCRIPT_NAME']

$_SERVER['SCRIPT_NAME'] returns the path or location of the script being executed. 

Syntax

<?php

echo $_SERVER['SCRIPT_NAME'];

?>

Example

<?php    

    echo "Example of SCRIPT_NAME<br><br>";

    echo "The path of this script is: <br><br>";    

    // returns the path

    echo $_SERVER['SCRIPT_NAME'];

    echo '<br>';

?>

In the above example, it returns the current script’s path. The name of the script file is “index.php”.

• $_SERVER['REQUEST_URI']

$_SERVER['REQUEST_URI'] is used to get the URI of the existing page. Uniform Resource Identifier or URI represents the lines that mainly begin with HTTP that you usually see on the webserver. For example, “http://www.w3.org/” is the URI of the World Wide Web’s home page.

Syntax

<?php

echo $_SERVER['REQUEST_URI'];

?>

Example

<?php    

    echo "Example of REQUEST_URI<br><br>";

    echo "The URI this page is: <br><br>";    

    // returns the URI

    echo $_SERVER['REQUEST_URI'];

    echo '<br>'; 

?>

In the above example, the URI of the current page is returned. If the complete path of a web page is “http://www.abc.com/test/index.php”, then the URI will be returned as “/test/index.php”.

Final Thoughts!

In this article, you learned about the superglobal called $_SERVER in PHP. You saw its use and also explored how to use $_SERVER in the PHP program. Finally, you saw the different parameters that can be used along with the $_SERVER in PHP to achieve different goals.  

If you want to begin your journey with PHP and learn the basic as well as advanced concepts and topics in PHP, you should check out Simplilearn’s online course on PHP training. By the end of this training, you will be able to build dynamic end-to-end web applications with PHP. You can also check out this starter guide video on PHP. 

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