how to get the absolute path of an included file?

Hello, Here are the two scripts. The result is 'var is' rather than 'var is foo'. My suspect is I did not set the file path right in 'include'. So in file2.php, how should I get the actual absolute path it really gets for file1.php? Is it stored in some environment variable or something? I'd appreciate any help. file1.php == <?php $var = 'foo'; ?> == file2.php == <?php include '/some/path/file1.php'; echo "var is $var"; ?> == Thanks, Bing