diff --git a/classes/context/Context.class.php b/classes/context/Context.class.php
index 7a1e4a854..02930c18f 100644
--- a/classes/context/Context.class.php
+++ b/classes/context/Context.class.php
@@ -499,7 +499,7 @@ class Context
 		{
 			$config = Rhymix\Framework\Config::getAll();
 		}
-		if (!count($config))
+		if (!is_array($config) || !count($config))
 		{
 			self::$_instance->db_info = self::$_instance->db_info ?: new stdClass;
 			return;
diff --git a/classes/db/DB.class.php b/classes/db/DB.class.php
index 244f73f1d..e325b185d 100644
--- a/classes/db/DB.class.php
+++ b/classes/db/DB.class.php
@@ -902,7 +902,7 @@ class DB
 	 */
 	public function _dbInfoExists()
 	{
-		return ($this->master_db && count($this->slave_db));
+		return $this->master_db ? true : false;
 	}
 
 	/**
diff --git a/classes/db/queryparts/Query.class.php b/classes/db/queryparts/Query.class.php
index 229a3b8fc..968bb2b3e 100644
--- a/classes/db/queryparts/Query.class.php
+++ b/classes/db/queryparts/Query.class.php
@@ -149,7 +149,9 @@ class Query extends BaseObject
 
 	function setColumnList($columnList)
 	{
+		if (!is_array($this->columnList)) return;
 		$this->columnList = $columnList;
+		
 		if(count($this->columnList) > 0)
 		{
 			$selectColumns = array();
diff --git a/common/functions.php b/common/functions.php
index 0e14e729d..1100a75f5 100644
--- a/common/functions.php
+++ b/common/functions.php
@@ -691,4 +691,21 @@ function is_empty_html_content($str)
 	$str = strip_tags($str, '<img><audio><video><iframe><object><embed>');
 	$str = utf8_trim(utf8_clean(html_entity_decode($str, ENT_QUOTES, 'UTF-8')));
 	return $str === '';
-}
\ No newline at end of file
+}
+
+/**
+ * Check if there is 'is_countable' function (PHP 7.3)
+ * If there is no 'is_countable' function, define it to check for Countable objects.
+ * 
+ * cf. https://wiki.php.net/rfc/is-countable
+ * 
+ * @param string $str The input string
+ * @return bool
+**/
+if (!function_exists('is_countable'))
+{
+    function is_countable($var)
+	{
+        return is_array($var) || $var instanceof Countable;
+    }
+}
diff --git a/common/js/xml_handler.js b/common/js/xml_handler.js
index 24207788a..7495dbd93 100644
--- a/common/js/xml_handler.js
+++ b/common/js/xml_handler.js
@@ -241,11 +241,12 @@
 			
 			// If the response contains an error, display the error message.
 			if(data.error != "0" && data.error > -1000) {
+				// Should not display the error message when the callback function returns false.
+				if ($.isFunction(callback_error) && callback_error(data) === false) {
+					return;
+				}
 				if(data.error == -1 && data.message == "admin.msg_is_not_administrator") {
 					alert("You are not logged in as an administrator.");
-					if ($.isFunction(callback_error)) {
-						callback_error(data);
-					}
 					return;
 				} else {
 					if (data.message) {
@@ -253,9 +254,6 @@
 					} else {
 						alert("AJAX communication error while requesting " + request_info);
 					}
-					if ($.isFunction(callback_error)) {
-						callback_error(data);
-					}
 					return;
 				}
 			}
diff --git a/layouts/simple_world/layout.html b/layouts/simple_world/layout.html
index 23adb481c..4096eeb86 100644
--- a/layouts/simple_world/layout.html
+++ b/layouts/simple_world/layout.html
@@ -151,7 +151,7 @@
 <footer class="layout_frame layout_footer">
 	<div class="layout_footer layout_canvas">
 		<!--// Footer Menu -->
-		<nav class="layout_menu" id="layout_fnb" cond="count($FNB->list) > 0">
+		<nav class="layout_menu" id="layout_fnb" cond="is_countable($FNB->list) && count($FNB->list)">
 			<ul>
 				<li loop="$FNB->list=>$key1,$val1" class="footer_menu">
 					<a href="{$val1['href']}" target="_blank"|cond="$val1['open_window']=='Y'"><span>{$val1['link']}</span></a>
@@ -160,7 +160,7 @@
 		</nav>
 		<!--// Footer Menu -->
 		<!--// Language -->
-		<div class="layout_language" cond="count($lang_supported) > 1">
+		<div class="layout_language" cond="is_countable($lang_supported) && count($lang_supported) > 1">
 			<button type="button" class="toggle">Language: {$lang_supported[$lang_type]}</button>
 			<ul class="selectLang">
 				<li loop="$lang_supported=>$key,$val" cond="$key!= $lang_type"><button type="button" onclick="doChangeLangType('{$key}');return false;">{$val}</button></li>
diff --git a/m.layouts/colorCode/layout.html b/m.layouts/colorCode/layout.html
index 2355c477c..d1b196382 100644
--- a/m.layouts/colorCode/layout.html
+++ b/m.layouts/colorCode/layout.html
@@ -35,7 +35,7 @@
 	<li><a href="{getUrl('act','dispMemberLoginForm')}" >{$lang->cmd_login}...</a></li>
 	<!--@end-->
 	<li><a href="{getUrl('m',0)}">PC</a></li>
-	<li class="lang off" cond="count($lang_supported)>1">
+	<li class="lang off" cond="is_countable($lang_supported) && count($lang_supported)>1">
 		<a href="#" onclick="return false;" title="{$lang_type}">{$lang_supported[$lang_type]} <i class="icon_arr_draw"></i></a>
 		<ul class="lang_lst">
 		<!--@foreach($lang_supported as $key=>$val)-->
diff --git a/m.layouts/default/layout.html b/m.layouts/default/layout.html
index 3af2ff8e7..f3ae6c537 100644
--- a/m.layouts/default/layout.html
+++ b/m.layouts/default/layout.html
@@ -28,6 +28,6 @@
 	<li class="fl"><a href="{getUrl('act','dispMemberLoginForm')}">{$lang->cmd_login}...</a></li>
 	<!--@end-->
 	<li class="fr"><a href="{getUrl('m',0)}">PC</a></li>
-	<li class="fr" cond="count($lang_supported)>1"><a href="{getUrl('act','dispModuleChangeLang','oldact',$act)}">LANG</a></li>
+	<li class="fr" cond="is_countable($lang_supported) && count($lang_supported)>1"><a href="{getUrl('act','dispModuleChangeLang','oldact',$act)}">LANG</a></li>
 </ul>
 <p class="cr">{$layout_info->index_title}<!--@if(!$layout_info->index_title)-->{Context::getSiteTitle()}<!--@end--></p>
diff --git a/m.layouts/simpleGray/layout.html b/m.layouts/simpleGray/layout.html
index f2e93728d..9f06d775d 100644
--- a/m.layouts/simpleGray/layout.html
+++ b/m.layouts/simpleGray/layout.html
@@ -14,6 +14,6 @@
 	<li class="fl"><a href="{getUrl('act','dispMemberLoginForm')}">{$lang->cmd_login}...</a></li>
 	<!--@end-->
 	<li class="fr"><a href="{getUrl('m',0)}">PC</a></li>
-	<li class="fr" cond="count($lang_supported)>1"><a href="{getUrl('act','dispModuleChangeLang','oldact',$act)}">LANG</a></li>
+	<li class="fr" cond="is_countable($lang_supported) && count($lang_supported)>1"><a href="{getUrl('act','dispModuleChangeLang','oldact',$act)}">LANG</a></li>
 </ul>
 <p class="cr">{$layout_info->index_title}</p>
diff --git a/modules/module/module.controller.php b/modules/module/module.controller.php
index a0c9c06ba..3b2132044 100644
--- a/modules/module/module.controller.php
+++ b/modules/module/module.controller.php
@@ -955,7 +955,7 @@ class moduleController extends module
 	{
 		$this->deleteModuleExtraVars($module_srl);
 		getDestroyXeVars($obj);
-		if(!$obj || !count($obj)) return;
+		if(!$obj || !is_countable($obj) || !count($obj)) return;
 
 		foreach($obj as $key => $val)
 		{
diff --git a/widgets/content/skins/simple_rectangle/content.html b/widgets/content/skins/simple_rectangle/content.html
index 8c0ed9561..76b708923 100644
--- a/widgets/content/skins/simple_rectangle/content.html
+++ b/widgets/content/skins/simple_rectangle/content.html
@@ -1,4 +1,4 @@
-<load target="./js/content_widget.js" cond="$widget_info->page_count || count($widget_info->tab)" />
+<load target="./js/content_widget.js" cond="$widget_info->page_count || (is_countable($widget_info->tab) && count($widget_info->tab))" />
 <!--// Check layout. If it is Simple World, select layout primary colors as a primary color of this skin -->
 {@$layout_info = Context::get('layout_info')}
 <block cond="$layout_info->extra_var->primary_color->type === 'select' || $layout_info->extra_var->customized_primary_color->type === 'colorpicker'">
@@ -71,14 +71,16 @@
 <div class="widgetContainer">
 	<div class="simple_content">
 		<section class="simple_content">
-			<!--@if($widget_info->tab_type  == "tab_left" && count($widget_info->tab) > 1)-->
-				<!--#include("./_tab_left.html")-->
-			<!--@elseif($widget_info->tab_type == "tab_top" && count($widget_info->tab) > 1)-->
-				<!--#include("./_tab_top.html")-->
-			<!--@else-->
-				<!--@if($widget_info->tab_type  == "tab_left" || $widget_info->tab_type == "tab_top")-->
+			<!--@if(is_countable($widget_info->tab))-->
+				<!--@if($widget_info->tab_type  == "tab_left" && count($widget_info->tab) > 1)-->
+					<!--#include("./_tab_left.html")-->
+				<!--@elseif($widget_info->tab_type == "tab_top" && count($widget_info->tab) > 1)-->
+					<!--#include("./_tab_top.html")-->
+				<!--@elseif($widget_info->tab_type  == "tab_left" || $widget_info->tab_type == "tab_top")-->
 					{@$widget_info->content_items = $widget_info->tab[0]->content_items}
+					<!--#include("./_tab_none.html")-->
 				<!--@end-->
+			<!--@else-->
 				<!--#include("./_tab_none.html")-->
 			<!--@end-->
 		</section>