Array and Select Options
probably not really drupal realated. But here you go:

Drupal.behaviors.mywebform = {
  attach: function (context, settings) {
    $.ajax({
        url:'/devtest/sites/democities.php',
        type:'POST',
        dataType: 'json',
        success: function( json ) {
            // if #edit-submitted-info-city is not a select you will have to make it one, or take the select that is in, or create one select in it.
            $('#edit-submitted-info-city').append('&lt;select&gt;').attr('id', 'stackexchangeExample');

            $.each(json, function(i, value) {
                $('#stackexchangeExample').append($('&lt;option&gt;').text(value.city).attr('value', value.city));
            });
        }
    });
}};


you might want to make sure that you run this only once, adjust the creation of the select element accordingly. or add a once() implementation