diff --git a/js/config.js b/js/config.js
index d6afdf1ab0..71d4d05ec3 100644
--- a/js/config.js
+++ b/js/config.js
@@ -734,7 +734,7 @@ function savePrefsToLocalStorage(form)
             submit_get_json: true
         },
         success: function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 window.localStorage.config = data.prefs;
                 window.localStorage.config_mtime = data.mtime;
                 window.localStorage.config_mtime_local = (new Date()).toUTCString();
diff --git a/js/db_operations.js b/js/db_operations.js
index a0e0dcd1fd..a9395e91fa 100644
--- a/js/db_operations.js
+++ b/js/db_operations.js
@@ -52,7 +52,7 @@ AJAX.registerOnload('db_operations.js', function () {
         $form.PMA_confirm(question, $form.attr('action'), function (url) {
             PMA_ajaxShowMessage(PMA_messages.strRenamingDatabases, false);
             $.get(url, $("#rename_db_form").serialize() + '&is_js_confirmed=1', function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxShowMessage(data.message);
                     PMA_commonParams.set('db', data.newname);
 
@@ -86,7 +86,7 @@ AJAX.registerOnload('db_operations.js', function () {
         $.get($form.attr('action'), $form.serialize(), function (data) {
             // use messages that stay on screen
             $('div.success, div.error').fadeOut();
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 if ($("#checkbox_switch").is(":checked")) {
                     PMA_commonParams.set('db', data.newname);
                     PMA_commonActions.refreshMain(false, function () {
@@ -112,7 +112,7 @@ AJAX.registerOnload('db_operations.js', function () {
         PMA_prepareForAjaxRequest($form);
         PMA_ajaxShowMessage(PMA_messages.strChangingCharset);
         $.get($form.attr('action'), $form.serialize() + "&submitcollation=1", function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 PMA_ajaxShowMessage(data.message);
             } else {
                 PMA_ajaxShowMessage(data.error, false);
diff --git a/js/db_search.js b/js/db_search.js
index e430a68314..d1351b5ee0 100644
--- a/js/db_search.js
+++ b/js/db_search.js
@@ -46,7 +46,7 @@ function loadResult(result_path, table_name, link)
         $('#table-link').attr({"href" : 'sql.php?' + link }).text(table_name);
         var url = result_path + "#sqlqueryresults";
         $.get(url, {'ajax_request': true, 'is_js_confirmed': true}, function (data) {
-            if (data.success) {
+            if (typeof data !== 'undefined' && data.success) {
                 $('#browse-results').html(data.message);
                 $('html, body')
                     .animate({
@@ -85,7 +85,7 @@ function deleteResult(result_path, msg)
             var url = result_path + "#result_query, #sqlqueryform";
             $.get(url, {'ajax_request': true, 'is_js_confirmed': true},
                 function (data) {
-                    if (data.success) {
+                    if (typeof data !== 'undefined' && data.success) {
                         $('#sqlqueryform').html(data.sql_query);
                         /** Refresh the search results after the deletion */
                         document.getElementById('buttonGo').click();
@@ -203,7 +203,7 @@ AJAX.registerOnload('db_search.js', function () {
 
         var url = $form.serialize() + "&submit_search=" + $("#buttonGo").val();
         $.post($form.attr('action'), url, function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 // found results
                 $("#searchresults").html(data.message);
 
diff --git a/js/db_structure.js b/js/db_structure.js
index fca48a4bbc..d5144e9c24 100644
--- a/js/db_structure.js
+++ b/js/db_structure.js
@@ -295,7 +295,7 @@ AJAX.registerOnload('db_structure.js', function () {
             PMA_ajaxShowMessage(PMA_messages.strProcessingRequest);
 
             $.get(url, {'is_js_confirmed' : 1, 'ajax_request' : true}, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxShowMessage(data.message);
                     // Adjust table statistics
                     var $tr = $this_anchor.closest('tr');
@@ -355,7 +355,7 @@ AJAX.registerOnload('db_structure.js', function () {
             var $msg = PMA_ajaxShowMessage(PMA_messages.strProcessingRequest);
 
             $.get(url, {'is_js_confirmed' : 1, 'ajax_request' : true}, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxShowMessage(data.message);
                     toggleRowColors($curr_row.next());
                     $curr_row.hide("medium").remove();
@@ -391,7 +391,7 @@ AJAX.registerOnload('db_structure.js', function () {
             PMA_ajaxShowMessage(PMA_messages.strDeletingTrackingData);
 
             $.get(url, {'is_js_confirmed': 1, 'ajax_request': true}, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     var $tracked_table = $curr_tracking_row.parents('table');
                     var table_name = $curr_tracking_row.find('td:nth-child(2)').text();
 
diff --git a/js/functions.js b/js/functions.js
index 449d4e15bc..150671c452 100644
--- a/js/functions.js
+++ b/js/functions.js
@@ -271,7 +271,7 @@ function PMA_display_git_revision()
             "ajax_request": true
         },
         function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 $(data.message).insertAfter('#li_pma_version');
             }
         }
@@ -2402,7 +2402,7 @@ AJAX.registerOnload('functions.js', function () {
             PMA_prepareForAjaxRequest($form);
             //User wants to submit the form
             $.post($form.attr('action'), $form.serialize() + "&do_save_data=1", function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     $('#properties_message')
                      .removeClass('error')
                      .html('');
@@ -2483,7 +2483,7 @@ AJAX.registerOnload('functions.js', function () {
 
         //User wants to add more fields to the table
         $.post($form.attr('action'), $form.serialize() + "&submit_num_fields=1", function (data) {
-            if (data.success) {
+            if (typeof data !== 'undefined' && data.success) {
                 $("#page_content").html(data.message);
                 PMA_highlightSQL($('#page_content'));
                 PMA_verifyColumnsProperties();
@@ -2545,7 +2545,7 @@ AJAX.registerOnload('functions.js', function () {
         var $form = $(this);
         PMA_prepareForAjaxRequest($form);
         $.post($form.attr('action'), $form.serialize() + "&submit_copy=Go", function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 if ($form.find("input[name='switch_to_new']").prop('checked')) {
                     PMA_commonParams.set(
                         'db',
@@ -2579,7 +2579,7 @@ AJAX.registerOnload('functions.js', function () {
         var tbl = $form.find('input[name=new_name]').val();
         PMA_prepareForAjaxRequest($form);
         $.post($form.attr('action'), $form.serialize() + "&submit_move=1", function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 PMA_commonParams.set('db', db);
                 PMA_commonParams.set('table', tbl);
                 PMA_commonActions.refreshMain(false, function () {
@@ -2606,7 +2606,7 @@ AJAX.registerOnload('functions.js', function () {
             PMA_prepareForAjaxRequest($form);
             var tbl = $tblNameField.val();
             $.post($form.attr('action'), $form.serialize(), function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_commonParams.set('table', tbl);
                     PMA_commonActions.refreshMain(false, function () {
                         $('#page_content').html(data.message);
@@ -2638,14 +2638,14 @@ AJAX.registerOnload('functions.js', function () {
                 $('html, body').animate({ scrollTop: 0 });
             }
             var $temp_div;
-            if (data.success === true && data.sql_query !== undefined) {
+            if (typeof data !== 'undefined' && data.success === true && data.sql_query !== undefined) {
                 PMA_ajaxShowMessage(data.message);
                 $("<div id='sqlqueryresults' class='ajax'></div>").prependTo("#page_content");
                 $("#sqlqueryresults").html(data.sql_query);
                 PMA_highlightSQL($('#page_content'));
                 scrollToTop();
-            } else if (data.success === true) {
-                $temp_div = $("<div id='temp_div'></div>");
+            } else if (typeof data !== 'undefined' && data.success === true) {
+                var $temp_div = $("<div id='temp_div'></div>");
                 $temp_div.html(data.message);
                 var $success = $temp_div.find("#result_query .success");
                 PMA_ajaxShowMessage($success);
@@ -2689,7 +2689,7 @@ AJAX.registerOnload('functions.js', function () {
         $(this).PMA_confirm(question, $(this).attr('href'), function (url) {
             PMA_ajaxShowMessage(PMA_messages.strProcessingRequest);
             $.get(url, {'is_js_confirmed': '1', 'ajax_request': true}, function (data) {
-                if (data.success) {
+                if (typeof data !== 'undefined' && data.success) {
                     //Database deleted successfully, refresh both the frames
                     PMA_reloadNavigation();
                     PMA_commonParams.set('db', '');
@@ -2794,7 +2794,7 @@ AJAX.registerOnload('functions.js', function () {
             $the_form.append('<input type="hidden" name="ajax_request" value="true" />');
 
             $.post($the_form.attr('action'), $the_form.serialize() + '&change_pw=' + this_value, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     $("#page_content").prepend(data.message);
                     PMA_highlightSQL($('#page_content'));
                     $("#change_password_dialog").hide().remove();
@@ -2811,7 +2811,7 @@ AJAX.registerOnload('functions.js', function () {
             $(this).dialog('close');
         };
         $.get($(this).attr('href'), {'ajax_request': true}, function (data) {
-            if (data.success) {
+            if (typeof data !== 'undefined' && data.success) {
                 $('<div id="change_password_dialog"></div>')
                 .dialog({
                     title: PMA_messages.strChangePassword,
@@ -3342,7 +3342,7 @@ function indexEditorDialog(url, title, callback_success, callback_failure)
             if ($("#sqlqueryresults").length !== 0) {
                 $("#sqlqueryresults").remove();
             }
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 PMA_ajaxShowMessage(data.message);
                 if ($('#result_query').length) {
                     $('#result_query').remove();
@@ -3392,7 +3392,7 @@ function indexEditorDialog(url, title, callback_success, callback_failure)
     };
     var $msgbox = PMA_ajaxShowMessage();
     $.get("tbl_indexes.php", url, function (data) {
-        if (data.success === false) {
+        if (typeof data !== 'undefined' && data.success === false) {
             //in the case of an error, show the error message returned.
             PMA_ajaxShowMessage(data.error, false);
         } else {
@@ -3614,7 +3614,7 @@ var toggleButton = function ($obj) {
             addClass = 'on';
         }
         $.post(url, {'ajax_request': true}, function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 PMA_ajaxRemoveMessage($msg);
                 $container
                 .removeClass(removeClass)
@@ -3762,7 +3762,7 @@ AJAX.registerOnload('functions.js', function () {
         $.get(
             $('#update_recent_tables').attr('href'),
             function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     $('#pma_recent_list').html(data.list);
                 }
             }
@@ -3962,7 +3962,7 @@ AJAX.registerOnload('functions.js', function () {
 
             var $msgbox = PMA_ajaxShowMessage(PMA_messages.strProcessingRequest);
             $.get(url, {'is_js_confirmed': '1', 'ajax_request': true}, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxRemoveMessage($msgbox);
                     // Table deleted successfully, refresh both the frames
                     PMA_reloadNavigation();
@@ -3995,7 +3995,7 @@ AJAX.registerOnload('functions.js', function () {
 
             var $msgbox = PMA_ajaxShowMessage(PMA_messages.strProcessingRequest);
             $.get(url, {'is_js_confirmed': '1', 'ajax_request': true}, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxRemoveMessage($msgbox);
                     // Table deleted successfully, refresh both the frames
                     PMA_reloadNavigation();
@@ -4032,7 +4032,7 @@ AJAX.registerOnload('functions.js', function () {
                 if ($("#result_query").length !== 0) {
                     $("#result_query").remove();
                 }
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxShowMessage(data.message);
                     $("<div id='sqlqueryresults'></div>").prependTo("#page_content");
                     $("#sqlqueryresults").html(data.sql_query);
@@ -4275,7 +4275,7 @@ function PMA_createViewDialog($this)
     var $msg = PMA_ajaxShowMessage();
     var syntaxHighlighter = null;
     $.get($this.attr('href') + '&ajax_request=1&ajax_dialog=1', function (data) {
-        if (data.success === true) {
+        if (typeof data !== 'undefined' && data.success === true) {
             PMA_ajaxRemoveMessage($msg);
             var buttonOptions = {};
             buttonOptions[PMA_messages.strGo] = function () {
@@ -4285,7 +4285,7 @@ function PMA_createViewDialog($this)
                 $msg = PMA_ajaxShowMessage();
                 $.get('view_create.php', $('#createViewDialog').find('form').serialize(), function (data) {
                     PMA_ajaxRemoveMessage($msg);
-                    if (data.success === true) {
+                    if (typeof data !== 'undefined' && data.success === true) {
                         $('#createViewDialog').dialog("close");
                         $('#result_query').html(data.message);
                         PMA_reloadNavigation();
diff --git a/js/gis_data_editor.js b/js/gis_data_editor.js
index e8860242df..2074b57f49 100644
--- a/js/gis_data_editor.js
+++ b/js/gis_data_editor.js
@@ -147,7 +147,7 @@ function loadGISEditor(value, field, type, input_name, token) {
         'token' : token,
         'ajax_request': true
     }, function (data) {
-        if (data.success === true) {
+        if (typeof data !== 'undefined' && data.success === true) {
             $gis_editor.html(data.gis_editor);
             initGISEditorVisualization();
             prepareJSVersion();
@@ -197,7 +197,7 @@ function insertDataAndClose() {
     var input_name = $form.find("input[name='input_name']").val();
 
     $.post('gis_data_editor.php', $form.serialize() + "&generate=true&ajax_request=true", function (data) {
-        if (data.success === true) {
+        if (typeof data !== 'undefined' && data.success === true) {
             $("input[name='" + input_name + "']").val(data.result);
         } else {
             PMA_ajaxShowMessage(data.error, false);
@@ -248,7 +248,7 @@ AJAX.registerOnload('gis_data_editor.js', function () {
     $('#gis_editor').find("input[type='text']").live('change', function () {
         var $form = $('form#gis_data_editor_form');
         $.post('gis_data_editor.php', $form.serialize() + "&generate=true&ajax_request=true", function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 $('#gis_data_textarea').val(data.result);
                 $('#placeholder').empty().removeClass('hasSVG').html(data.visualization);
                 $('#openlayersmap').empty();
@@ -269,7 +269,7 @@ AJAX.registerOnload('gis_data_editor.js', function () {
         var $form = $('form#gis_data_editor_form');
 
         $.post('gis_data_editor.php', $form.serialize() + "&get_gis_editor=true&ajax_request=true", function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 $gis_editor.html(data.gis_editor);
                 initGISEditorVisualization();
                 prepareJSVersion();
diff --git a/js/indexes.js b/js/indexes.js
index 17ba19d0ec..6d2e4dcaa3 100644
--- a/js/indexes.js
+++ b/js/indexes.js
@@ -514,7 +514,7 @@ AJAX.registerOnload('indexes.js', function () {
         $anchor.PMA_confirm(question, $anchor.attr('href'), function (url) {
             var $msg = PMA_ajaxShowMessage(PMA_messages.strDroppingPrimaryKeyIndex, false);
             $.get(url, {'is_js_confirmed': 1, 'ajax_request': true}, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxRemoveMessage($msg);
                     var $table_ref = $rows_to_hide.closest('table');
                     if ($rows_to_hide.length == $table_ref.find('tbody > tr').length) {
diff --git a/js/makegrid.js b/js/makegrid.js
index 77404c2b77..c88cd63d5a 100644
--- a/js/makegrid.js
+++ b/js/makegrid.js
@@ -970,7 +970,7 @@ function PMA_makegrid(t, enableResize, enableReorder, enableVisib, enableGridEdi
                         }, function (data) {
                             g.lastXHR = null;
                             $editArea.removeClass('edit_area_loading');
-                            if (data.success === true) {
+                            if (typeof data !== 'undefined' && data.success === true) {
                                 $td.data('original_data', data.value);
                                 $(g.cEdit).find('.edit_box').val(data.value);
                                 $editArea.append('<textarea></textarea>');
@@ -1258,7 +1258,7 @@ function PMA_makegrid(t, enableResize, enableReorder, enableVisib, enableGridEdi
                             $('div.save_edited').removeClass('saving_edited_data')
                                 .find('input').removeProp('disabled');  // enable the save button back
                         }
-                        if (data.success === true) {
+                        if (typeof data !== 'undefined' && data.success === true) {
                             PMA_ajaxShowMessage(data.message);
 
                             // update where_clause related data in each edited row
diff --git a/js/navigation.js b/js/navigation.js
index 3cbae9ff74..f5971c507f 100644
--- a/js/navigation.js
+++ b/js/navigation.js
@@ -250,7 +250,7 @@ $(function () {
         $.ajax({
             url: $(this).attr('href') + '&ajax_request=true',
             success: function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_reloadNavigation();
                 } else {
                     PMA_ajaxShowMessage(data.error);
@@ -264,7 +264,7 @@ $(function () {
         event.preventDefault();
         var $msg = PMA_ajaxShowMessage();
         $.get($(this).attr('href') + '&ajax_request=1', function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 PMA_ajaxRemoveMessage($msg);
                 var buttonOptions = {};
                 buttonOptions[PMA_messages.strClose] = function () {
@@ -298,7 +298,7 @@ $(function () {
             url: $(this).attr('href') + '&ajax_request=true',
             success: function (data) {
                 PMA_ajaxRemoveMessage($msg);
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     $tr.remove();
                     PMA_reloadNavigation();
                 } else {
@@ -438,7 +438,7 @@ function expandTreeNode($expandElem, callback) {
         $throbber.insertBefore($icon);
 
         loadChildNodes($expandElem, function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 var $destination = $expandElem.closest('li');
                 $icon.removeClass('ic_b_plus').addClass('ic_b_minus');
                 $children = $destination.children('div.list_container');
@@ -535,7 +535,7 @@ function loadChildNodes($expandElem, callback) {
 
     var url = $('#pma_navigation').find('a.navigation_url').attr('href');
     $.get(url, params, function (data) {
-        if (data.success === true) {
+        if (typeof data !== 'undefined' && data.success === true) {
             $expandElem.addClass('loaded');
             $destination.find('div.list_container').remove(); // FIXME: Hack, there shouldn't be a list container there
             $destination.append(data.message);
@@ -767,7 +767,7 @@ function PMA_reloadNavigation(callback) {
     });
     var url = $('#pma_navigation').find('a.navigation_url').attr('href');
     $.post(url, params, function (data) {
-        if (data.success) {
+        if (typeof data !== 'undefined' && data.success) {
             $('#pma_navigation_tree').html(data.message).children('div').show();
             if ($('#pma_navigation_tree').hasClass('synced')) {
                 PMA_showCurrentNavigation();
@@ -818,7 +818,7 @@ function PMA_navigationTreePagination($this) {
     }
     $.post(url, params, function (data) {
         PMA_ajaxRemoveMessage($msgbox);
-        if (data.success) {
+        if (typeof data !== 'undefined' && data.success) {
             if (isDbSelector) {
                 var val = PMA_fastFilter.getSearchClause();
                 $('#pma_navigation_tree')
diff --git a/js/server_databases.js b/js/server_databases.js
index 59dc03de68..a780888733 100644
--- a/js/server_databases.js
+++ b/js/server_databases.js
@@ -64,7 +64,7 @@ AJAX.registerOnload('server_databases.js', function () {
                 PMA_ajaxShowMessage(PMA_messages.strProcessingRequest, false);
 
                 $.post(url, function (data) {
-                    if (data.success === true) {
+                    if (typeof data !== 'undefined' && data.success === true) {
                         PMA_ajaxShowMessage(data.message);
 
                         var $rowsToRemove = $form.find('tr.removeMe');
@@ -109,7 +109,7 @@ AJAX.registerOnload('server_databases.js', function () {
         PMA_prepareForAjaxRequest($form);
 
         $.post($form.attr('action'), $form.serialize(), function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 PMA_ajaxShowMessage(data.message);
 
                 //Append database's row to table
diff --git a/js/server_privileges.js b/js/server_privileges.js
index f0feca1b4c..50160922c9 100644
--- a/js/server_privileges.js
+++ b/js/server_privileges.js
@@ -122,7 +122,7 @@ function addUser($form)
 
     //We also need to post the value of the submit button in order to get this to work correctly
     $.post($form.attr('action'), $form.serialize() + "&adduser_submit=" + $("input[name=adduser_submit]").val(), function (data) {
-        if (data.success === true) {
+        if (typeof data !== 'undefined' && data.success === true) {
             // Refresh navigation, if we created a database with the name
             // that is the same as the username of the new user
             if ($('#add_user_dialog #createdb-1:checked').length) {
@@ -257,7 +257,7 @@ AJAX.registerOnload('server_privileges.js', function () {
         var $msgbox = PMA_ajaxShowMessage();
 
         $.get($(this).attr("href"), {'ajax_request': true}, function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 $('#page_content').hide();
                 var $div = $('#add_user_dialog');
                 if ($div.length === 0) {
@@ -314,7 +314,7 @@ AJAX.registerOnload('server_privileges.js', function () {
             PMA_ajaxShowMessage(PMA_messages.strRemovingSelectedUsers);
 
             $.post(url, $form.serialize() + "&delete=" + $thisButton.val() + "&ajax_request=true", function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxShowMessage(data.message);
                     // Refresh navigation, if we droppped some databases with the name
                     // that is the same as the username of the deleted user
@@ -364,7 +364,7 @@ AJAX.registerOnload('server_privileges.js', function () {
                 'token': token
             },
             function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxRemoveMessage($msg);
                     var buttonOptions = {};
                     buttonOptions[PMA_messages.strGo] = function () {
@@ -377,7 +377,7 @@ AJAX.registerOnload('server_privileges.js', function () {
                             $('#changeUserGroupDialog').find('form').serialize() + '&ajax_request=1',
                             function (data) {
                                 PMA_ajaxRemoveMessage($message);
-                                if (data.success === true) {
+                                if (typeof data !== 'undefined' && data.success === true) {
                                     $("#usersForm")
                                         .find('.current_row')
                                         .removeClass('current_row')
@@ -449,7 +449,7 @@ AJAX.registerOnload('server_privileges.js', function () {
                 'token': token
             },
             function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     $('#page_content').hide();
                     var $div = $('#edit_user_dialog');
                     if ($div.length === 0) {
@@ -524,7 +524,7 @@ AJAX.registerOnload('server_privileges.js', function () {
         }
 
         $.post($t.attr('action'), $t.serialize() + '&' + curr_submit_name + '=' + curr_submit_value, function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 $('#page_content').show();
                 $("#edit_user_dialog").remove();
 
@@ -606,7 +606,7 @@ AJAX.registerOnload('server_privileges.js', function () {
             $(this.form).prop('action'),
             $(this.form).serialize() + '&submit_mult=export&ajax_request=true',
             function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     var $ajaxDialog = $('<div />')
                     .append(data.message)
                     .dialog({
@@ -662,7 +662,7 @@ AJAX.registerOnload('server_privileges.js', function () {
             $(this).dialog("close");
         };
         $.get($(this).attr('href'), {'ajax_request': true}, function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 var $ajaxDialog = $('<div />')
                 .append(data.message)
                 .dialog({
@@ -704,7 +704,7 @@ AJAX.registerOnload('server_privileges.js', function () {
         event.preventDefault();
         var $msgbox = PMA_ajaxShowMessage();
         $.get($(this).attr('href'), {'ajax_request' : true}, function (data) {
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 PMA_ajaxRemoveMessage($msgbox);
                 // This form is not on screen when first entering Privileges
                 // if there are more than 50 users
diff --git a/js/server_status_monitor.js b/js/server_status_monitor.js
index 24274a3d07..0fc927c9fc 100644
--- a/js/server_status_monitor.js
+++ b/js/server_status_monitor.js
@@ -700,7 +700,7 @@ AJAX.registerOnload('server_status_monitor.js', function () {
             $.get('server_status_monitor.php?' + PMA_commonParams.get('common_query'), vars,
                 function (data) {
                     var logVars;
-                    if (data.success === true) {
+                    if (typeof data !== 'undefined' && data.success === true) {
                         logVars = data.message;
                     } else {
                         return serverResponseError();
@@ -1360,7 +1360,7 @@ AJAX.registerOnload('server_status_monitor.js', function () {
             requiredData: JSON.stringify(runtime.dataList)
         }, function (data) {
             var chartData;
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 chartData = data.message;
             } else {
                 return serverResponseError();
@@ -1604,7 +1604,7 @@ AJAX.registerOnload('server_status_monitor.js', function () {
             function (data) {
                 var logData;
                 var dlgBtns = {};
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     logData = data.message;
                 } else {
                     return serverResponseError();
@@ -1993,7 +1993,7 @@ AJAX.registerOnload('server_status_monitor.js', function () {
             database: db
         }, function (data) {
             var i;
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 data = data.message;
             }
             if (data.error) {
diff --git a/js/server_variables.js b/js/server_variables.js
index 56370b8a70..b0f9eb532b 100644
--- a/js/server_variables.js
+++ b/js/server_variables.js
@@ -123,7 +123,7 @@ AJAX.registerOnload('server_variables.js', function () {
                 type: 'getval',
                 varName: varName
             }, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     var $editor = $('<div />', {'class': 'serverVariableEditor'})
                         .append($myCancelLink)
                         .append(' ')
diff --git a/js/tbl_chart.js b/js/tbl_chart.js
index c909141242..14dcd8c81b 100644
--- a/js/tbl_chart.js
+++ b/js/tbl_chart.js
@@ -414,7 +414,7 @@ $("#tblchartform").live('submit', function (event) {
     PMA_prepareForAjaxRequest($form);
 
     $.post($form.attr('action'), $form.serialize(), function (data) {
-        if (data.success === true) {
+        if (typeof data !== 'undefined' && data.success === true) {
             $('.success').fadeOut();
             if (typeof data.chartData != 'undefined') {
                 chart_data = jQuery.parseJSON(data.chartData);
diff --git a/js/tbl_relation.js b/js/tbl_relation.js
index 99ffb87f51..c487365fe4 100644
--- a/js/tbl_relation.js
+++ b/js/tbl_relation.js
@@ -86,7 +86,7 @@ function getDropdownValues($dropdown) {
         datatype: 'json',
         success: function (data) {
             PMA_ajaxRemoveMessage($msgbox);
-            if (data.success) {
+            if (typeof data !== 'undefined' && data.success) {
                 // if the changed dropdown is a database selector
                 if (foreignTable === null) {
                     // set values for table and column dropdowns
diff --git a/js/tbl_select.js b/js/tbl_select.js
index 474d1c114c..7b796c6443 100644
--- a/js/tbl_select.js
+++ b/js/tbl_select.js
@@ -140,7 +140,7 @@ AJAX.registerOnload('tbl_select.js', function () {
 
         $.post($search_form.attr('action'), values, function (data) {
             PMA_ajaxRemoveMessage($msgbox);
-            if (data.success === true) {
+            if (typeof data !== 'undefined' && data.success === true) {
                 if (typeof data.sql_query !== 'undefined') { // zero rows
                     $("#sqlqueryresults").html(data.sql_query);
                 } else { // results found
diff --git a/js/tbl_structure.js b/js/tbl_structure.js
index bf5f626036..c62c72b6fa 100644
--- a/js/tbl_structure.js
+++ b/js/tbl_structure.js
@@ -216,7 +216,7 @@ AJAX.registerOnload('tbl_structure.js', function () {
         $(this).PMA_confirm(question, $(this).attr('href'), function (url) {
             var $msg = PMA_ajaxShowMessage(PMA_messages.strDroppingColumn, false);
             $.get(url, {'is_js_confirmed' : 1, 'ajax_request' : true, 'ajax_page_request' : true}, function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxRemoveMessage($msg);
                     if ($('#result_query').length) {
                         $('#result_query').remove();
@@ -271,7 +271,7 @@ AJAX.registerOnload('tbl_structure.js', function () {
             $.get(url,
                 {'is_js_confirmed' : 1, 'ajax_request' : true, 'index_change' : true},
                 function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxRemoveMessage($msg);
                     $(this).remove();
                     if (typeof data.reload != 'undefined') {
@@ -320,7 +320,7 @@ AJAX.registerOnload('tbl_structure.js', function () {
             $.get(url,
                 {'is_js_confirmed' : 1, 'ajax_request' : true, 'index_change' : true},
                 function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxRemoveMessage($msg);
                     if ($('#result_query').length) {
                         $('#result_query').remove();
@@ -364,7 +364,7 @@ AJAX.registerOnload('tbl_structure.js', function () {
             $.get(url,
                 {'is_js_confirmed' : 1, 'ajax_request' : true, 'index_change' : true},
                 function (data) {
-                if (data.success === true) {
+                if (typeof data !== 'undefined' && data.success === true) {
                     PMA_ajaxRemoveMessage($msg);
                     if ($('#result_query').length) {
                         $('#result_query').remove();
diff --git a/js/tbl_zoom_plot_jqplot.js b/js/tbl_zoom_plot_jqplot.js
index a19a4ebc8d..5057ec4435 100644
--- a/js/tbl_zoom_plot_jqplot.js
+++ b/js/tbl_zoom_plot_jqplot.js
@@ -399,7 +399,7 @@ AJAX.registerOnload('tbl_zoom_plot_jqplot.js', function () {
                     'sql_query' : sql_query,
                     'inline_edit' : false
                 }, function (data) {
-                    if (data.success === true) {
+                    if (typeof data !== 'undefined' && data.success === true) {
                         $('#sqlqueryresults').html(data.sql_query);
                         $("#sqlqueryresults").trigger('appendAnchor');
                     } else {