server variables as in $_SERVER[] are very helpful in building scripts which run on different servers.
instead of hardcoding variables these might do the trick

this snippet will produce a list of all available server variables

“server variables” makes use of the built-in PHP functions chr( ) and highlight_string( ).

01 <?php
02 
03 $str = '<?php
04  
05     // all available server variables on '.$_SERVER['HTTP_HOST'].'
06 ';
07  
08 // list all available server variables
09 foreach($_SERVER as $key=>$value)
10 {
11     $str .= '
12     $_SERVER[\''.$key.'\'] = \''.$value.'\';';
13 }
14  
15 $str .= '
16  
17 '.chr(63).'>
18 ';
19  
20 // output the string as highlighted PHP source
21 highlight_string($str);
22  
23 ?>