Help with the copy command...

Okay, this seems like a ridiculously easy question which shouldn't even need asking, but I'm having trouble getting the builtin copy command to work properly. It seems to work fine as long as I feed it a full constant string path for each argument (ie - in the form "/the/path/to/the/file"). However, if I try to feed it two variables as the arguments, it craps out somewhere along the line. Here are the two different sets of calls I'm making: These two work perfectly: copy("/usr/local/apache/htdocs/ipreg2/crons/regservice_rep/snapshot.baseline", "/usr/local/apache/htdocs/ipreg2/crons/regservice_rep/snapshot.baseline.bak") ; copy("/usr/local/apache/htdocs/ipreg2/crons/regservice_rep/lastrun.timestamp", "/usr/local/apache/htdocs/ipreg2/crons/regservice_rep/lastrun.timestamp.bak"); These two fail: $l_stLastRun = "/usr/local/apache/htdocs/ipreg2/crons/regservice_rep/lastrun.timestamp"; $l_stSnapshotBase = "/usr/local/apache/htdocs/ipreg2/crons/regservice_rep/snapshot.baseline"; copy($l_stSnapshotBase, $l_stSnapshotBase.".bak"); copy($l_stLastRun, $l_stLastRun.".bak"); Can anyone offer any insight on what the problem might be with this? The "unlink" function seems to accept the variable inputs with absolutely no problem, so I can't understand the discrepancy between the two. Thanks in advance. Tim