First time PHP user question

Hello List. I have been playing around with PHP, running a few tutorials and I came across an error message I could not resolve. The tutorial is Generating One Time URL's by Oreilly: http://www.oreillynet.com/pub/a/php/2002/12/05/one_time_URLs.html Basically the PHP code is supposed to read from a text file and write to a text file and serve a text file all located in the "tmp" directory of the server. However, I receive the error that the referenced files in the PHP code could not be found: "Warning: readfile(/tmp/secret_file.txt) [function.readfile]: failed to open stream: No such file or directory in/home/mysite/myfolder/get_file.php on line 67" Line 66 and 67 look like this: $secretfile = "/tmp/secret_file.txt"; readfile($secretfile); However, in the tmp folder, I have created a simple text file called "secret_file.txt" so I know it exists and it has the permissions set to 644, so it should be readable. Can someone point out to me what I am doing wrong? Thanks, --Rick