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/**
 * Custom Generic Validation Function
 * @param type $type : Validation Type
 * @param type $field : On which validation to be done
 * @param type $value : Value of field
 * @param type $message : Message text Optional
 * @return type
 */
function custom_validate($type, $field, $value, $message = NULL) {
  switch ($type) {

    case numeric_check:
      $rex_mobile = "/[^0-9]/";
      if (preg_match($rex_mobile, $value)) {
        $default_message = 'Please enter a valid contact number.';
        $error = TRUE;
      }
      break;

    case empty_check:
      if (empty($value)) {
        $default_message = 'Highlighted field cannot be empty.';
        $error = TRUE;
      }
      break;

    default:
      break;
  }

  if ($error == TRUE) {
    $message = empty($message) ? $default_message : $message;
    form_set_error($field, $message);
  }
  return;
}