// Lookup pre-existing records
$preexisting = civicrm_api3('entity_tag', 'get', $baseParams);
$preexisting = array_column($preexisting['values'], 'tag_id');
// Lookup pre-existing records
$preexisting = civicrm_api3('entity_tag', 'get', $baseParams);
$preexisting = array_column($preexisting['values'], 'tag_id');