In php, should I return false, null, or an empty array in a method that would usually return an array?

Question

I\'ve found several responses to this, but none pertaining to PHP (which is an extremely weak typed language):

With regards to PHP, is it appropriate to return

Answer 1

I would strongly discourage to return mixed type return values. I consider it to be so much a problem, that i wrote a small article about not returning mixed typed values.

To answer your question, return an empty array. Below you can find a small example, why returning other values can cause problems:

// This kind of mixed-typed return value (boolean or string),
// can lead to unreliable code!
function precariousCheckEmail($input)
{
  if (filter_var($input, FILTER_VALIDATE_EMAIL))
    return true;
  else
    return 'E-Mail address is invalid.';
}

// All this checks will wrongly accept the email as valid!
$result = precariousCheckEmail('nonsense');
if ($result == true)
  print('OK'); // -> OK will be given out

if ($result)
  print('OK'); // -> OK will be given out

if ($result === false)
  print($result);
else
  print('OK'); // -> OK will be given out

if ($result == false)
  print($result);
else
  print('OK'); // -> OK will be given out

Hope this helps preventing some misunderstandings.