What are some potential limitations when trying to access system variables (environment variables) in PHP on a Windows server?

When trying to access system variables (environment variables) in PHP on a Windows server, one potential limitation is that the $_SERVER superglobal may not contain the variables you are looking for due to differences in how Windows handles environment variables compared to Unix-based systems. To overcome this limitation, you can use the getenv() function in PHP to directly access the environment variables on a Windows server.

$variable_value = getenv('VARIABLE_NAME');
echo $variable_value;