get_term() does not verify for valid output from wpdb::get_row()

[johncoswell]

It's possible for wpdb::get_row() to return invalid data from a request to get_term(), yet there's no type checking done on the return value from wpdb::get_row(), which can cause PHP to raise warnings when returning something other than an object. Something similar to this should fix the issue (/wp-includes/taxonomy.php, ~line 332):

if (is_object($_term)) {
  if ($output == OBJECT) {
    ...
  } elseif (...) {
    ...
  }
} else {
  return $_term; // or maybe WP_Error
}

[scribu]

This is the documented return value:

 * @return mixed|null|WP_Error Term Row from database. Will return null if $term is empty. If taxonomy does not exist then WP_Error will be returned.

So it's the expected behaviour. Could you paste a specific error and in what context you got it?

[johncoswell]

The error message: get_object_vars() expects parameter 1 to be object, null given in wp-includes\taxonomy.php on line 335

The function get_category() is being called with $object set to ARRAY_A. If the requested category ID that is passed to get_category(), which is subsequently passed to wpdb::get_row(), does not exist in the database, or some other failure occurs within wpdb::get_row(), wpdb::get_row() can return a non-object value such as null. When the code falls through to the section returning the output, and ARRAY_A or ARRAY_N is provided as $object, this non-object value will be passed to get_object_vars(), raising the warning. This warning is not raised in any other state for $object, as those cause $_term to be returned untouched.

[scribu]

Type check before doing anything else

[scribu]

Oh, I see. You're right. It should check for a null value before filtering, etc.

See attached patch.

[johncoswell]

That should do it. Thanks.

[ryan]

(In [12200]) Return null if no term queried. fixes #11112