I can create paths with no problem, but I want to know which of these 3 methods is the most rock solid and reliable and will work on the most servers.

Right now I am using method 1 in my script and some users are having path issues. I just want the method that will work on any version of php and almost any server config. 

1.  <?php echo $_SERVER['DOCUMENT_ROOT']; ?>

2.  <?php echo getcwd(); ?>

3.  <?php echo dirname(__FILE__); ?>

Thank you so much for any expertise you can provide about this!

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