populating a form field with output from a custom plugin function

Question

I need to add a unique string to a form as an identifier for customers. I have created some functions that will output a string of characters. I want to populate a form field with that using a shortcode. Not having much luck.

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');

And from my hidden input field (within Gravity Forms config tool) I am using [ABC_form_number length="13" char="num" case="false"]. Not seeing any data in the invoicenum field.

EDIT: Updated the code sample. I was able to apply the WP shortcode and output a string from my plugin to a post. Trying to use the approach to populate a field in a Gravity Forms form has not worked. Here's a link to some documentation at Gravity Forms for something that looks related. No luck applying this for a fix. https://docs.gravityforms.com/gform_shortcode_form_property/

Answer 1

You can pre-populate a field with gform_field_value_$parameter_name hook, where $parameter_name is the name of the field/parameter. So, for example if you added that to your code:

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"]');
}

(Note: Allow field to be populated dynamically option needs to be enabled)