Using Environment Variables in PHP

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  • Service Type: Grid
    • Difficulty: Medium
    • Time Needed: 10
    • Tools Required: None

Environment variable definition

PHP environment variables allow your scripts to glean certain types of data dynamically from the server. This supports script flexibility in a potentially changing server environment. For example, the SITE_HTMLROOT variable provided by (mt) Media Temple will automatically provide the correct path to your document root on any Grid server, without necessitating any changes in your script. (mt) Media Temple provides several dozen variables like this for your convenience.


This article is provided as a courtesy. Installing, configuring, and troubleshooting third-party applications is outside the scope of support provided by (mt) Media Temple. Please take a moment to review the Statement of Support.

Use and examples

You can access these variables using the $_SERVER and $_ENV arrays.

For example, if you want to use the SITE_HTMLROOT variable mentioned above, you can create a variable in your PHP script similar to the following:

Filename: environment.php

$site_path_var = $_SERVER["SITE_HTMLROOT"];

This will create a variable with a value similar to the following:


If you want to test the output of the variable, add an echo statement to your PHP script. For example:

Filename: environment.php

$site_path_var = $_SERVER["SITE_HTMLROOT"];
echo $site_path_var;

Now visit your script in your browser to see the output.


$_SERVER and $_ENV are PHP superglobal arrays. They do not have to be declared as global variables. Do NOT put the following line in your file:

Filename: environment.php

global $_SERVER;

Practical use

On the Grid, it is particularly helpful to use a few select environment variables, for three reasons. First, if you ever decide to re-use a script on a different domain on the Grid, you won't have to change all your variables. Second, the variables are often more convenient than the long path and server names used for the Grid architecture. Third, the Grid load-balancing occasionally requires sites and databases to be shifted to different physical machines, which can change your environment. This is not a common occurrence, but it is an essential part of Grid functionality.

    The full path to your site's document root, returns output like /home/00000/domains/
  • $_ENV["DATABASE_SERVER"] - The internal database server name, returns output like

Complete list of provided variables

Create a phpinfo.php page to view all of your (mt) Media Temple-provided variables. See our "How can I create a phpinfo.php page?" article for details, paying attention the PHP Variables section of the page for the relevant information.


Setting your own variables


On the Grid, you can set your own environment variables that will last within the session that created them. For example, if you want to use a custom environment variable in a script, you can add the following lines to create and then use a variable:

Filename: environment.php

$new_variable_var = $_ENV["MYENV"];

Note: These environment variables will not last outside the session in which they were created.

In .htaccess

You can also have Apache set environment variables for use in your scripts, via a .htaccess file, using SetEnv or in Rewrite rules. These variables must start with 'HTTP_' for security purposes.

SetEnv HTTP_MY_VARIABLE "my value"

User-friendly server information

If you want to view system information in a more user-friendly format, check your Grid Server Guide. The Database Connections and System Paths sections contain useful information about your server environment.