Ajax : Why success displays 0?

I use ajax with jquery and when I tried to display the result in popup. Then alert always displays 0

success : function(results) { 
alert(results); }

EDIT :

 var dataToSend = {
    action:"ACTIO开发者_如何学PythonN_NAME",
    id : "12"
  };
  url_action = 'http://www.______.com/wp-admin/admin-ajax.php';
  $.ajax({
          url: url_action,
          type:'POST',
          data: dataToSend,
          success:function(results)
          {
             alert(results);
          }
   });

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Try to add die(); or exit(); at the very last line of the function.

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May be you are trying without login. so you need to use this action.

add_action('wp_ajax_nopriv_my_action', 'my_action_callback');

you will get response. :)

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I had a similar issue with admin-ajax.php returning 0, even i had die().

My problem was that the add_action was declared in a file not loaded default by plugin.

Anyway, if you have problem also check in browser what __.com/wp-admin/admin-ajax.php?action=youraction returns.

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Found it.

It need to add die(); before the end of my own ajax function in function.php.

Because there is one line of script in admin-ajax.php after my own ajax_action that says: die('0'); So we need to die() script before die('0').

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I was adding the "action" incorrectly. You have to prefix your action with wp_ajax_gd_.

add_action('wp_ajax_gd_[ACTION NAME]', '[CALLBACK FUNCTION NAME]')

and in the JS jQuery post:

var data = {
    'action': '[ACTION NAME]',
};

I found Wordpress' documentation very unclear about this part.

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That's probably because the server side script you are calling with AJAX returns 0 (the one you have specified in the url property).

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Make sure the action_name is ok. If it's not found in functions.php you will get 0 as the result.

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In your PHP function, make sure you're using echo instead of return.

This was happening for me in a WordPress theme.

function doAjax() {
    $result = getPosts();
    echo json_encode($result, true);
    die();
}

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I had the same issue. I'd forgotten to enable the plugin. After enabling the plugin I received the expected data.

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Adding die(); at the end of your function can solve it. Thank you.

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Those who get error 0 :), action => 'action'

var data = {'action': 'my_action', 'data': form_data };

$.post(ajaxurl, data, function(response) { alert(response);});