Unable to open and write files from certain virtual host

[phpmaven]

I have following lines of code: 
$handle = fopen("/usr/local/www/logs/test.log", "a"); 
fwrite($handle, "this is a test"); 
fclose($handle); 

I have an Apache server with several virtual hosts running. One virtual host can run this code with no problem and the file gets created and written to. The same exact code fails on a different virtual host with "Warning: fopen(/usr/local/www/logs/test.log): failed to open stream: No such file or directory in..." 

I'm totally baffled as to what the problem could be. 

Thanks, 

Mark

 

[iarp]

Are both virtual hosts running as the same user/group or are you modify those with AssignUserId?