多个组合框与事件更改

I have a problem when populate combobox with data from query. And when I change the combobox, I want to set value in the textbox or hidden with selected onchange combobox.

When the first combobox that work but when I change the second combobox, not set value to textbox or hidden value.

<script type='text/javascript'>
  $(function() {
    $('#myselect').change(function() { 
      var x = $(this).val(); 
      $('#myhidden').val(x); 
    });
  });
</script>

<input type='text' id='myhidden' value=''>

<?php    
    $result2 = mysql_query("select id_users, fullname from users where status='1'");  
    echo'<select name="iduserowner" class=form-control id=myselect>';
    while($data2 = mysql_fetch_array($result2)) {
      echo '<option  value="'.$data2['id_users'].'">'.$data2['fullname'].'</option>';
    }    
    echo '</select>';    
?>

as I understand you want to put your selected value into your hidden input. try this:

<?php $sql = "SELECT id_users, fullname
               FROM users
               WHERE status = '1'";

        $res = mysql_query( $sql );
    ?>

    <input type="text" id="myhidden" value="">
    <select onChange="hideSelected();" name="iduserowner" class="form-control" id="myselect" >

    <? while( $result = mysql_fetch_array( $res, MYSQL_ASSOC )){ ?>

        <option value="<?= $result[ 'id_users' ]; ?>"><?= $result[ 'fullname' ]; ?></option>

    <? } ?>
    </select>



    <script>

    function hideSelected(){

        $("#myhidden").val( $("#myselect option:selected").val() );
    }

    </script>