Return PHP error constant (such as E_USER_ERROR) from function, or use trigger_error?

Question

Which would you recommend?

1. Return an error code, such as E_USER_ERROR from a function, and determine proper message higher up:

   function currentScriptFilename()
   {
     if(!isset($_SERVER['SCRIPT_FILENAME']))
     {
       //This?
       return E_USER_ERROR;
     }
     else
     {
       $url = $_SERVER['SCRIPT_FILENAME'];
       $exploded = explode('/', $url);
       return end($exploded);
     }
   }
   

2. Execute trigger_error() from the function, with a specific error message:

   function currentScriptFilename()
   {
     if(!isset($_SERVER['SCRIPT_FILENAME']))
     {
       //Or this?
       trigger_error('$_SERVER[\'SCRIPT_FILENAME\'] is not set.', E_USER_ERROR);
     }
     else
     {
       $url = $_SERVER['SCRIPT_FILENAME'];
       $exploded = explode('/', $url);
       return end($exploded);
     }
   }
   

I am not sure if I will regret having put a bunch of error messages in my functions further down the line, since I would like to use them for other projects.

Or, would you recommend something totally different?

Answer 1

3.Use exceptions.

Answer 2

If this is the route you are going, I'd rather recommend throwing Exceptions rather then returing an E_ERROR (E_USER_ERROR should be used), as this is just an integer, and possibly a totally valid return for your function.

Advantages:
- Throwing of an Exception cannot be interpreted as anything else then an error by mistake.
- You keep the possibility to add a descriptive error message, even though you don't handle the error at that point/
- You keep a backtrace in your Exception.
- You can catch specific exceptions at specific points, making the decision where in your project a specific type of error should be handled a lot easier.

Answer 3

If not using exceptions which you should be, use trigger_error().

If it is an error you'd like to deal with, try returning FALSE like a lot of the in built functions do.

If you do use exceptions, catch them like this

try {
    whatever()
} catch (Exception $e) {
    // handle however
}

Answer 4

Do not mix the matters.
Error notification and error handling are different tasks.

You have to use both methods simultaneously.
If you think that $_SERVER['SCRIPT_FILENAME'] availability is worth an error message, you can use trigger error. However PHP itself will throw a notice if you won't check it.

If you want to handle this error, just check this function's return value.
But I would not create a special function for this task.

So,

if (!$filename = basename($_SERVER['SCRIPT_FILENAME']) {
  //  do whatever you want to handle this error.
}

would be enough

Exceptions could be useful to handle errors, to know if we had any errors occurred.

A simple example:

try {
  $filename = basename($_SERVER['SCRIPT_FILENAME']) 
  if (!$filename) throw new Exception("no filename");

  $data = get_some_data_from_db() or throw new Exception("no data");

  $template = new Template();
 //Exception could be thrown inside of Template class as well.
}
catch (Exception $e) {
  //if we had any errors
  show_error_page();
}
$template->show();