Dynamically populate a Contact Form 7 dropdown list form db and add custom validation

gistfile1.txt

add this shortcode in contact from
[select upcoming-gigs data:gigs]

add this code in functions.php
<?php
add_filter('wpcf7_form_tag_data_option', function($n, $options, $args) {
    global $wpdb;
  $result = $wpdb->get_results("SELECT DATE_FORMAT(termin, '%d.%m.%Y') as termin FROM einweihungen where termin >= CURDATE() ORDER BY einweihungen.termin ASC;");

   $optionsarr = array();
     foreach ($result as $termin) {
        $optionsarr[]=$termin->termin;
     }
  if (in_array('gigs', $options)){
    $gigs =$optionsarr;
    return $gigs;
  }
  return $n;
}, 10, 3);
add_filter( 'wpcf7_validate_select', 'wpharvest_custom_validation_select', 20, 2 );
/**
 * Go through all the select fields
 */
function wpharvest_custom_validation_select( $result, $tag ) {

   if ( 'upcoming-gigs' == $tag->name && empty( $_POST['upcoming-gigs'] )) {
         $result->invalidate($tag, "This field is required.");
      }

    return $result;
}