I just troubleshooted a linux server issue where my HTTP error log files grow so fast. I found many lines similar like this one:
[Sat May 12 21:45:37 2009] [error] [client xx.xx.xxx.xxx] PHP Warning: fread(): supplied argument is not a valid stream resource in /htdocs/libraries/tcpdf/tcpdf.php on line 3915
This seamed to be a permission issues. I already had set 777 to:
but I found another cache folder which must be set to 777:
this seamed to solve the issue.