Paul Osman

Derick Rethans has a post about PHP’s “shut-up” operator (@) and why it should be avoided. He outlines a fairly common debugging scenario and gives some “under-the-hood” explanations on why that particular operator sucks. I couldn’t agree more (that it should be avoided) and I want to go further and talk about something that has always bugged me about that operator. In my opinion, it’s a hackish, band-aid fix to a much larger, much more worrisome problem: horrendous API design.

First, a disclaimer. I know that there are some historical reasons for a lot of these things (i.e. Exceptions not appearing until PHP5) but that doesn’t change the current reality. Consider for instance filesystem functions in the standard extension:

$lines = file("/tmp/file.txt");

If the file “/tmp/file.txt” does not exist, depending on your php.ini settings (because display_errors should always be ‘Off’ on production systems), you may get something similar to the following output:

Warning: file(/tmp/file.txt) [function.file]: failed to open stream: No such file or directory in /path/to/your/docroot/test.php on line 3

Now the proper thing to do of course would be to verify up front that the file exists and is readable with a call to is_readable() or something similar, but imagine this is a case where there is no way to determine ahead of time if a warning or error will be generated (Derick mentions silencing network errors with stream_socket_client() as one example). In this case, you might be tempted to use the shut-up operator and depend on the return value as the one true way to see if something was succesful or not.

Now compare this with what languages like Python (for example) do, If you were to write similar code in Python:

fp = file("/tmp/file.txt")

If the file did not exist, you’ll get an IOError which, if left uncaught, will result in the following being written to standard error:

Traceback (most recent call last):
  File "test.py", line 1, in <module>
IOError: [Errno 2] No such file or directory: '/tmp/test.txt'

The difference here of course is that an IOError can be caught, ignored or whatever best suits your needs. It’s a part of the language, the API is not just spewing out garbage to standard output or standard error. More importantly, having a function (or technically a constructor) like file() throw an exception follows a consistent design philosophy whereas PHP’s error system always leaves me guessing or consulting the docs.

I guess what I’m saying is that I think the shut-up operator is just one of those signs that PHP is suffering from some serious cruft and I don’t think those kinds of things bode well for a language.