Merge mutiple fields into one

I have 2 option cck fields, one is a predefined list, the other is a text field. Both are set to unlimited number of values. I first tried to use array_merge, since it would be a more "elegant" solution; but I couldn't make it fly. This was my first attempt.

// set temp variable
$count = 0;

// put array into computed field array pt1
foreach (element_children($node->field_option) as $key) {
	$node_field[$count]['value'] = $node->field_option[$key]['value'];
	$count++;
}

// put array into computed field array pt2
foreach (element_children($node->field_option_list) as $key) {
	$node_field[$count]['value'] = $node->field_option_list[$key]['value'];
	$count++;
}

To make this into a comma separated list, here is the code. This works with "Store using the database", while the top one doesn't for some reason. This is what I'm using now

// set temp variable
$temp = array();

// put array into computed field array pt1
foreach (element_children($node->field_option) as $key) {
	$temp[] = $node->field_option[$key]['value'];
}

// put array into computed field array pt2
foreach (element_children($node->field_option_list) as $key) {
	$temp[] = $node->field_option_list[$key]['value'];
}

//kill empty values in the array
foreach ($temp as $key => $value) {
	if (is_null($value) || $value=="") {
		unset($temp[$key]);
	}
} 

//implode to comma list
$node_field[0]['value'] = implode(', ', $temp);