Description:
------------
The file_put_contents function doesn't return anything on an error, it would be better if for example: on a permission error, I could catch an error instead of a big message and no result

Reproduce code:
---------------
if(file_put_contents("./file", " ") === FALSE)
{
  exit("error, could not write to file");
}
else
{
  echo "Yay, file is completed";
}


Expected result:
----------------
error, could not write to file

Actual result:
--------------
Warning: file_put_contents(./file) [function.file-put-contents]: failed to open stream: Permission denied in /var//www/test.php on line 2