diff --git a/src/Smarty.class.php b/src/Smarty.class.php
index 5351b57..0a47c83 100644
--- a/src/Smarty.class.php
+++ b/src/Smarty.class.php
@@ -107,7 +107,7 @@ class Smarty extends Smarty_Internal_TemplateBase
     /**
      * smarty version
      */
-    const SMARTY_VERSION = '4.3.0';
+    const SMARTY_VERSION = '4.4.1';
     /**
      * define variable scopes
      */
diff --git a/src/plugins/modifier.implode.php b/src/plugins/modifier.implode.php
new file mode 100644
index 0000000..679d71d
--- /dev/null
+++ b/src/plugins/modifier.implode.php
@@ -0,0 +1,15 @@
+<?php
+/**
+ * Smarty plugin
+ *
+ * @package    Smarty
+ * @subpackage PluginsModifier
+ */
+
+function smarty_modifier_implode($values, $separator = '')
+{
+	if (is_array($separator)) {
+		return implode((string) ($values ?? ''), (array) $separator);
+	}
+	return implode((string) ($separator ?? ''), (array) $values);
+}
diff --git a/src/plugins/modifiercompiler.json_encode.php b/src/plugins/modifiercompiler.json_encode.php
new file mode 100644
index 0000000..629277f
--- /dev/null
+++ b/src/plugins/modifiercompiler.json_encode.php
@@ -0,0 +1,11 @@
+<?php
+
+/**
+ * Smarty plugin
+ *
+ * @package    Smarty
+ * @subpackage PluginsModifierCompiler
+ */
+function smarty_modifiercompiler_json_encode($params) {
+	return 'json_encode(' . $params[0] . (isset($params[1]) ? ', (int) ' . $params[1] : '') . ')';
+}
diff --git a/src/plugins/modifiercompiler.lower.php b/src/plugins/modifiercompiler.lower.php
index 1f9cfb1..4144e56 100644
--- a/src/plugins/modifiercompiler.lower.php
+++ b/src/plugins/modifiercompiler.lower.php
@@ -22,7 +22,7 @@
 function smarty_modifiercompiler_lower($params)
 {
     if (Smarty::$_MBSTRING) {
-        return 'mb_strtolower(' . $params[ 0 ] . ', \'' . addslashes(Smarty::$_CHARSET) . '\')';
+        return 'mb_strtolower((string) ' . $params[ 0 ] . ', \'' . addslashes(Smarty::$_CHARSET) . '\')';
     }
     // no MBString fallback
     return 'strtolower((string) ' . $params[ 0 ] . ')';
diff --git a/src/plugins/modifiercompiler.substr.php b/src/plugins/modifiercompiler.substr.php
new file mode 100644
index 0000000..17721f5
--- /dev/null
+++ b/src/plugins/modifiercompiler.substr.php
@@ -0,0 +1,12 @@
+<?php
+
+/**
+ * Smarty plugin
+ *
+ * @package    Smarty
+ * @subpackage PluginsModifierCompiler
+ */
+function smarty_modifiercompiler_substr($params) {
+	return 'substr((string) ' . $params[0] . ', (int) ' . $params[1] .
+		(isset($params[2]) ? ', (int) ' . $params[2] : '') . ')';
+}
diff --git a/src/plugins/shared.escape_special_chars.php b/src/plugins/shared.escape_special_chars.php
index a204b09..355b02b 100644
--- a/src/plugins/shared.escape_special_chars.php
+++ b/src/plugins/shared.escape_special_chars.php
@@ -20,7 +20,7 @@
 function smarty_function_escape_special_chars($string)
 {
     if (!is_array($string)) {
-        $string = htmlspecialchars($string, ENT_COMPAT, Smarty::$_CHARSET, false);
+        $string = htmlspecialchars((string) $string, ENT_COMPAT, Smarty::$_CHARSET, false);
     }
     return $string;
 }
diff --git a/src/sysplugins/smarty_internal_compile_private_print_expression.php b/src/sysplugins/smarty_internal_compile_private_print_expression.php
index 96bd372..78f1c07 100644
--- a/src/sysplugins/smarty_internal_compile_private_print_expression.php
+++ b/src/sysplugins/smarty_internal_compile_private_print_expression.php
@@ -93,7 +93,7 @@ class Smarty_Internal_Compile_Private_Print_Expression extends Smarty_Internal_C
                 }
                 // autoescape html
                 if ($compiler->template->smarty->escape_html) {
-                    $output = "htmlspecialchars((string) {$output}, ENT_QUOTES, '" . addslashes(Smarty::$_CHARSET) . "')";
+                    $output = "htmlspecialchars((string) ({$output}), ENT_QUOTES, '" . addslashes(Smarty::$_CHARSET) . "')";
                 }
                 // loop over registered filters
                 if (!empty($compiler->template->smarty->registered_filters[ Smarty::FILTER_VARIABLE ])) {
diff --git a/src/sysplugins/smarty_internal_errorhandler.php b/src/sysplugins/smarty_internal_errorhandler.php
index 6f526c3..4ddcfcd 100644
--- a/src/sysplugins/smarty_internal_errorhandler.php
+++ b/src/sysplugins/smarty_internal_errorhandler.php
@@ -94,7 +94,7 @@ class Smarty_Internal_ErrorHandler
         }
 
         if ($this->allowUndefinedArrayKeys && preg_match(
-            '/^(Undefined index|Undefined array key|Trying to access array offset on value of type)/',
+            '/^(Undefined index|Undefined array key|Trying to access array offset on)/',
             $errstr
         )) {
             return; // suppresses this error