Warning: strcasecmp() expects parameter 1 to be string, array given in webform_conditional_operator_string_equal()

I'm not sure what the possible array structures are for the input values (haven't researched it), but the test in this patch looks brittle. As yourself, could any valid set of select keys match what you are testing to see if there are "other" values?

@Liam - In that case,

if (isset($input_values['select']) && is_array($input_values['select'])) // ... 

would be a better test, no?

My logic is that some module -- perhaps other than select_or_other -- might add nesting. Since what you want is the items under 'select', test for what you want to use and use it if it exists, rather than test for something else and infer that what you want should exist.

Yuck. My apologies for leading you astray.

There are 4 permutations of "multiple" and "select_or_other" (SOO), and they all look different. Using colors as an example, $input_values is:

Case 00: Neither Multiple Nor SOO:
An array with 0 => 'blue' (because a scalar string was converted to an array). Note that this is indexed by 0, rather than by the value, as is the case with multiple.

Case 01: Multiple only:
An array, with an entry for every option, with 'blue' => 'blue' (or 0, if not selected)

Case 10: SOO only:
An array, with two entries,
'other' => 'pink' and 'select' => 'select_or_other'
OR
'other' => 'pink' (or whatever value was last used, if any) and 'select' => 'blue'

Case 11: Both Multiple and SOO:
An array with two entries,
'other' => 'pink' (or whatever value was last used)
'select' => an array with an entry for every option as above, plus 'select_or_other'

An issue that I see is that case 01 looks exactly like case 10, if your webform component used a 'select' and 'other' as keys.

I think that testing for this in the equal operator function is the wrong place. I suggest "fixing" the values in _webform_client_form_rule_check(). Something like (untested):

        $source_values = array();
        if (isset($input_values[$source_cid])) {
          $component_value = $input_values[$source_cid];
          if ($source_component['type'] == 'select' && !empty($source_component['extra']['other_option'])) {
            $component_value = $component_value['select'];
          }
          $source_values = is_array($component_value) ? $component_value : array($component_value);
        }

I combined your patches into one commit, which went into 7.x-4.x and 8.x. Thank you very much.

Fixed a regression during preview.