$name = 'AppPromoZhongQiu2014ActiveStatusSelector';

echo cc_format($name);
function cc_format($name){
  $temp_array = array();
  for($i=0;$i<strlen($name);$i++){
    $ascii_code = ord($name[$i]);
    if($ascii_code >= 65 && $ascii_code <= 90){
      if($i == 0){
         $temp_array[] = chr($ascii_code + 32);
      }else{
        $temp_array[] = '_'.chr($ascii_code + 32);
      }
    }else{
      $temp_array[] = $name[$i];
    }
  }
  return implode('',$temp_array);
}