我需要在表单中添加一个唯一的字符串作为客户的标识符。我创建了一些输出字符串的函数。我想用一个短代码填充一个表单字段。运气不太好。

function ABC_validUniqueStr($attr){
  $length = $attr[\'length\']; // num (int)
  $char = $attr[\'char\']; // num, alpha, alphanum
  $case = $attr[\'case\']; // $case, true vary case, false upper case
  $validStr = \'\';
  do {
    // $string = ABC_form_number_alpha_numeric($length,$char,$case);
    $string = ABC_form_number_alpha_numeric($length=13,$char=\'num\',$case=false);
    $result = ABC_test_unique_form_number($string);
    if( $result[0]->count == \'0\' ) {
      $validStr = $string;
    }
  } while( $validStr == \'\' );
  return $validStr;
}

function ABC_form_number_alpha_numeric($length=13,$char=\'num\',$case=false) {
  $formNumberAlphaNumericStr = \'\';
  for( $i = 0; $i < $length; $i++ ){
    if( $char == \'num\' ) {
      $formNumberAlphaNumericStr .= rand(0,9);
    } elseif ( $char == \'alpha\' ) {
      $num = rand(0,25);
      $formNumberAlphaNumericStr .= ABC_retunAlpha($num,$case);
    } elseif ( $char == \'alphanum\' ) {
      $rando = rand(0,1);
      if( $rando == 0 ) {
        $formNumberAlphaNumericStr .= rand(0,9);
      } else {
        $num = rand(0,25);
        $formNumberAlphaNumericStr .= ABC_retunAlpha($num,$case);
      }
    } else {
      $formNumberAlphaNumericStr = \'error\';
    }
  }
  // var_dump($formNumberAlphaNumericStr);
  return $formNumberAlphaNumericStr;
}

function ABC_test_unique_form_number($str){
    global $wpdb;
  $sqlStr = "select count(*) as count from ".$wpdb->prefix."ABC_app_invoicenumber ";
  $sqlStr .= "where invoicenum = \'%s\'";
  $prepSql = $wpdb->prepare($sqlStr,$str);
  return $wpdb->get_results($prepSql);
}

function ABC_retunAlpha($num,$case){
  if( $num >= 0 && $num < 26 ) {
    $upperAlphaArr = array("A","B","C","D","E","F","G","H","I","J","K","L","M","N",
                                "O","P","Q","R","S","T","U","V","W",\'X\',"Y","Z");
    if( $case == 0 ) {
      return $upperAlphaArr[$num];
    } else {
      return strtolower($upperAlphaArr[$num]);
    }
  } else {
    return array(\'error\'=>\'num out of range\');
  }
}

add_shortcode(\'ABC_form_number\',\'ABC_validUniqueStr\');

add_filter( \'gform_shortcode_ABC_form_number\', \'ABC_validUniqueStr\');

从我的隐藏输入字段（在Gravity Forms config tool中），我正在使用[ABC_form_number length="13" char="num" case="false"]. 在invoicenum字段中看不到任何数据。

编辑：更新了代码示例。我能够应用WP短代码，并将插件中的字符串输出到帖子中。尝试使用这种方法在重力表单中填充字段是行不通的。这里有一个指向Gravity表单中一些文档的链接，这些文档看起来是相关的。无法将此应用于修复。https://docs.gravityforms.com/gform_shortcode_form_property/

add_filter(\'gform_field_value_invoice_numb\', \'my_func\');
function my_func( $value ) {
    return do_shortcode(\'[ABC_form_number length="13" char="num" case="false"]\');
}