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php – how to refresh Select2 dropdown menu after ajax loading different content?

Posted by: admin April 23, 2020 Leave a comment


I’m using Select2 in a combination of dropdown menus. I have one menu for “Countries” and one for “States/Provinces”. Depending on the country that is chosen, the “States/Provinces” dropdown changes in content. The states/provinces are pulled with ajax from a database and then displayed this way:

$display_output = '<select style="width:350px;" tabindex="2" name="state" id="state" data-placeholder="Choose a Country..."> ';
$display_output .= '<option value="" selected>Select a State</option> ';

while ($state_details = $this->fetch_array($sql_select_states))
    $display_output .= '<option value="' . $state_details['id'] . '" ' . (($selected_value == $state_details['id']) ? 'selected' : ''). '>' . $state_details['s.name'] . '</option>';

$display_output .= '</select>';

So far, so good. All the provinces change correctly, however when it initially loads, the Select2 shows “undefined” for the states dropdown, even though I have it set as

data-placeholder="Choose a Country..."

I’m assuming it could be because on loading, the country selected is “United States” and it populates a list of states but none of them is default or selected. Is there any other way to define a default value so that it doesn’t show “Undefined”?

And another (but less important) problem is that when someone chooses “United States” for example, and then chooses “Arizona”, if the person then changes to “Canada” as the country, the state of “Arizona” still stays but when opening the dropdown the provinces of Canada are selectable. Is there any way to return it to the default value temporarily when someone selects another country, until a province is chosen again?

My loading code is currently just:

$(document).ready(function() { $("#state").select2(); });
How to&Answers:

Select 3.*

Please see Update select2 data without rebuilding the control as this may be a duplicate. Another way is to destroy and then recreate the select2 element.



If you are having problems with resetting the state/region on country change try clearing the current value with

$("#dropdown").select2("val", "");

You can view the documentation here http://ivaynberg.github.io/select2/ that outlines nearly/all features. Select2 supports events such as change that can be used to update the subsequent dropdowns.

$("#dropdown").on("change", function(e) {});

Select 4.* Update

You can now update the data/list without rebuilding the control using:

    data: fromAccountData


It’s common for other components to be listening to the change event, or for custom event handlers to be attached that may have side effects. Select2 does not have a custom event (like select2:update) that can be triggered other than change. You can rely on jQuery’s event namespacing to limit the scope to Select2 though by triggering the *change.select2 event.

$('#state').trigger('change.select2'); // Notify only Select2 of changes


select2 has the placeholder parameter. Use that one

   placeholder: "Choose a Country"


Use the following script after appending your select.


Don’t use destroy.


Finally solved issue of reinitialization of select2 after ajax call.

You can call this in success function of ajax.

Note : Don’t forget to replace “.selector” to your class of <select class="selector"> element.


   placeholder: "Placeholder text",
   allowClear: true



Got the same problem in 11 11 19, so sorry for possible necroposting.
The only what helped was next solution:

var drop = $('#product_1');   // get our element, **must be unique**;
var settings = drop.attr('data-krajee-select2');  pick krajee attrs of our elem;
var drop_id = drop.attr('id');  // take id 
settings = window[settings];  // take previous settings from window;
drop.select2(settings);  // initialize select2 element with it;
$('.kv-plugin-loading').remove(); // remove loading animation;

It’s, maybe, not so good, nice and precise solution, and maybe I still did not clearly understood, how it works and why, but this was the only, what keeps my select2 dropdowns, gotten by ajax, alive.
Hope, this solution will be usefull or may push you in right decision in problem fixing


Initialize again select2 by new id or class like below

when the page load


call again when came by ajax after success ajax function