Robustly determine when strings are empty

D7 user_validate_name() is wrong.

0 should be a valid user name.

Yes #7 is exactly what I am suggesting.

form.inc checks for (strlen(trim($elements['#value'])) != 0) for required fields.

I don't know why the user code doesn't just leave it up to the forms layer to determine if it has been entered.

Code that needs to determine if an account is anonymous should examine uid, not name.

"0" being considered as an empty string is one of the reasons why people think PHP is a really crap language.

It makes sense to me to not allow people to use the username "0". I can't see a compelling reason to allow it. It seems like a hacker or troll thing to do. Normal use of Drupal usernames doesn't need this ability.

That said, I don't have my head wrapped around the backend implications of whatever choice.

Presuming $account->name or anything to be a string is a very dangerous assumption especially when dealing with zeroes. 0 == '', 0 == '0' and only '0' != ''. Use !== everywhere. It's faster to boot and leaves no doubts.

Let's not spill too much blood on this one. It's not important in the big picture and it's worth fixing.

I don't object to this patch, but it doesn't solve all the contrib uses of the same pattern that are out there. There's no reason to allow '0' as a username, and disallowing it prevents all those uses from being problematic.

format_username()'s technique of checking the username to determine if an account is a guest account is totally wrong. template_preprocess_username() does it correctly: checking the uid.

Okay - this snippet:

$string = '0';

if ($string) {
  return TRUE;
}

doesn't return TRUE!

Assuming that $string is actually a string, the correct way to test that it is empty is

if ($string == '')

To test if it is not empty:

if ($string != '')

A more elaborate test like strlen(trim($string)) == 0) could be used that would handle integer variables, but would be impracticable in theme templates and is unnecessary.

It seems that there are lots of places in core where empty strings are not being correctly tested for.

The attached patch builds on #12, fixing use of $title in bartik and fixing format_username().

#871160: Define programming best practices for determining if a string is empty

Hrm, #11 was too long ago. Then let me repeat: for readability and speed (and disambiguity) !== is much better than !=.

Yes, $variable !== '' will return FALSE if $variable is not a string.

I think this form should always be used if the assumption is that $variable should be a string.

Agreed with chx here, otherwise looks good.

Just browsing through Seven and Bartik, there are dozens of examples of

<?php if ($variable): ?>

where it should be

<?php if ($variable !== ''): ?>

Should this be standardized and fixed?

#871160: Define programming best practices for determining if a string is empty

Yes, yes, yes! It should definitely be standardized and fixed. I called for that at my Paris talk about how broken == is.