diff --git a/change_log.txt b/change_log.txt
index dbdbeb92..390eb471 100644
--- a/change_log.txt
+++ b/change_log.txt
@@ -1,4 +1,7 @@
 ===== 3.1.31-dev ===== (xx.xx.xx)
+ 01.09.2016
+  - performance require_once should be called only once for shared plugins https://github.com/smarty-php/smarty/issues/280
+  
  26.08.2016
   - bugfix change of 23.08.2016 failed on linux when use_include_path = true
 
diff --git a/libs/Smarty.class.php b/libs/Smarty.class.php
index c08eb747..ad1eb955 100644
--- a/libs/Smarty.class.php
+++ b/libs/Smarty.class.php
@@ -114,7 +114,7 @@ class Smarty extends Smarty_Internal_TemplateBase
     /**
      * smarty version
      */
-    const SMARTY_VERSION = '3.1.31-dev/7';
+    const SMARTY_VERSION = '3.1.31-dev/8';
 
     /**
      * define variable scopes
diff --git a/libs/plugins/block.textformat.php b/libs/plugins/block.textformat.php
index e9f5fe2d..e2c5e3de 100644
--- a/libs/plugins/block.textformat.php
+++ b/libs/plugins/block.textformat.php
@@ -38,6 +38,9 @@ function smarty_block_textformat($params, $content, $template, &$repeat)
     if (is_null($content)) {
         return;
     }
+    if (Smarty::$_MBSTRING && !is_callable('smarty_mb_wordwrap')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.mb_wordwrap.php');
+    }
 
     $style = null;
     $indent = 0;
@@ -92,7 +95,6 @@ function smarty_block_textformat($params, $content, $template, &$repeat)
         }
         // wordwrap sentences
         if (Smarty::$_MBSTRING) {
-            require_once(SMARTY_PLUGINS_DIR . 'shared.mb_wordwrap.php');
             $_paragraph = smarty_mb_wordwrap($_paragraph, $wrap - $indent, $wrap_char, $wrap_cut);
         } else {
             $_paragraph = wordwrap($_paragraph, $wrap - $indent, $wrap_char, $wrap_cut);
diff --git a/libs/plugins/function.html_checkboxes.php b/libs/plugins/function.html_checkboxes.php
index 33f2efe1..04ce4573 100644
--- a/libs/plugins/function.html_checkboxes.php
+++ b/libs/plugins/function.html_checkboxes.php
@@ -45,7 +45,9 @@
  */
 function smarty_function_html_checkboxes($params, $template)
 {
-    require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    if (!is_callable('smarty_function_escape_special_chars')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    }
 
     $name = 'checkbox';
     $values = null;
diff --git a/libs/plugins/function.html_image.php b/libs/plugins/function.html_image.php
index 854af61b..6da8fc54 100644
--- a/libs/plugins/function.html_image.php
+++ b/libs/plugins/function.html_image.php
@@ -38,7 +38,9 @@
  */
 function smarty_function_html_image($params, $template)
 {
-    require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    if (!is_callable('smarty_function_escape_special_chars')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    }
 
     $alt = '';
     $file = '';
diff --git a/libs/plugins/function.html_options.php b/libs/plugins/function.html_options.php
index 20e66771..bc8f36e0 100644
--- a/libs/plugins/function.html_options.php
+++ b/libs/plugins/function.html_options.php
@@ -35,7 +35,9 @@
  */
 function smarty_function_html_options($params)
 {
-    require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    if (!is_callable('smarty_function_escape_special_chars')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    }
 
     $name = null;
     $values = null;
diff --git a/libs/plugins/function.html_radios.php b/libs/plugins/function.html_radios.php
index 53b342de..6ef84328 100644
--- a/libs/plugins/function.html_radios.php
+++ b/libs/plugins/function.html_radios.php
@@ -45,7 +45,9 @@
  */
 function smarty_function_html_radios($params, $template)
 {
-    require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    if (!is_callable('smarty_function_escape_special_chars')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    }
 
     $name = 'radio';
     $values = null;
diff --git a/libs/plugins/function.html_select_date.php b/libs/plugins/function.html_select_date.php
index 8191700d..3a48da0b 100644
--- a/libs/plugins/function.html_select_date.php
+++ b/libs/plugins/function.html_select_date.php
@@ -6,15 +6,6 @@
  * @subpackage PluginsFunction
  */
 
-/**
- * @ignore
- */
-require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
-/**
- * @ignore
- */
-require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
-
 /**
  * Smarty {html_select_date} plugin
  * Type:     function<br>
@@ -52,6 +43,12 @@ require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
  */
 function smarty_function_html_select_date($params)
 {
+    if (!is_callable('smarty_function_escape_special_chars')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    }
+    if (!is_callable('smarty_make_timestamp')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
+    }
     // generate timestamps used for month names only
     static $_month_timestamps = null;
     static $_current_year = null;
diff --git a/libs/plugins/function.html_select_time.php b/libs/plugins/function.html_select_time.php
index 4a3639bc..89f0406f 100644
--- a/libs/plugins/function.html_select_time.php
+++ b/libs/plugins/function.html_select_time.php
@@ -6,15 +6,6 @@
  * @subpackage PluginsFunction
  */
 
-/**
- * @ignore
- */
-require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
-/**
- * @ignore
- */
-require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
-
 /**
  * Smarty {html_select_time} function plugin
  * Type:     function<br>
@@ -33,6 +24,12 @@ require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
  */
 function smarty_function_html_select_time($params)
 {
+    if (!is_callable('smarty_function_escape_special_chars')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');
+    }
+    if (!is_callable('smarty_make_timestamp')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
+    }
     $prefix = "Time_";
     $field_array = null;
     $field_separator = "\n";
diff --git a/libs/plugins/modifier.date_format.php b/libs/plugins/modifier.date_format.php
index ba716c47..a9b2997c 100644
--- a/libs/plugins/modifier.date_format.php
+++ b/libs/plugins/modifier.date_format.php
@@ -32,10 +32,6 @@ function smarty_modifier_date_format($string, $format = null, $default_date = ''
     if ($format === null) {
         $format = Smarty::$_DATE_FORMAT;
     }
-    /**
-     * require_once the {@link shared.make_timestamp.php} plugin
-     */
-    require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
     if ($string != '' && $string != '0000-00-00' && $string != '0000-00-00 00:00:00') {
         $timestamp = smarty_make_timestamp($string);
     } elseif ($default_date != '') {
@@ -44,7 +40,7 @@ function smarty_modifier_date_format($string, $format = null, $default_date = ''
         return;
     }
     if ($formatter == 'strftime' || ($formatter == 'auto' && strpos($format, '%') !== false)) {
-        if (DIRECTORY_SEPARATOR == '\\') {
+        if (Smarty::$_IS_WINDOWS) {
             $_win_from = array('%D', '%h', '%n', '%r', '%R', '%t', '%T');
             $_win_to = array('%m/%d/%y', '%b', "\n", '%I:%M:%S %p', '%H:%M', "\t", '%H:%M:%S');
             if (strpos($format, '%e') !== false) {
diff --git a/libs/plugins/modifier.escape.php b/libs/plugins/modifier.escape.php
index b9842aaf..9c247b93 100644
--- a/libs/plugins/modifier.escape.php
+++ b/libs/plugins/modifier.escape.php
@@ -116,7 +116,9 @@ function smarty_modifier_escape($string, $esc_type = 'html', $char_set = null, $
         case 'hexentity':
             $return = '';
             if (Smarty::$_MBSTRING) {
-                require_once(SMARTY_PLUGINS_DIR . 'shared.mb_unicode.php');
+                if (!is_callable('smarty_mb_to_unicode')) {
+                    require_once(SMARTY_PLUGINS_DIR . 'shared.mb_unicode.php');
+                }
                 $return = '';
                 foreach (smarty_mb_to_unicode($string, Smarty::$_CHARSET) as $unicode) {
                     $return .= '&#x' . strtoupper(dechex($unicode)) . ';';
@@ -135,7 +137,9 @@ function smarty_modifier_escape($string, $esc_type = 'html', $char_set = null, $
         case 'decentity':
             $return = '';
             if (Smarty::$_MBSTRING) {
-                require_once(SMARTY_PLUGINS_DIR . 'shared.mb_unicode.php');
+                if (!is_callable('smarty_mb_to_unicode')) {
+                    require_once(SMARTY_PLUGINS_DIR . 'shared.mb_unicode.php');
+                }
                 $return = '';
                 foreach (smarty_mb_to_unicode($string, Smarty::$_CHARSET) as $unicode) {
                     $return .= '&#' . $unicode . ';';
@@ -158,8 +162,9 @@ function smarty_modifier_escape($string, $esc_type = 'html', $char_set = null, $
 
         case 'mail':
             if (Smarty::$_MBSTRING) {
-                require_once(SMARTY_PLUGINS_DIR . 'shared.mb_str_replace.php');
-
+                if (!is_callable('smarty_mb_str_replace')) {
+                    require_once(SMARTY_PLUGINS_DIR . 'shared.mb_str_replace.php');
+                }
                 return smarty_mb_str_replace(array('@', '.'), array(' [AT] ', ' [DOT] '), $string);
             }
             // no MBString fallback
@@ -169,7 +174,9 @@ function smarty_modifier_escape($string, $esc_type = 'html', $char_set = null, $
             // escape non-standard chars, such as ms document quotes
             $return = '';
             if (Smarty::$_MBSTRING) {
-                require_once(SMARTY_PLUGINS_DIR . 'shared.mb_unicode.php');
+                if (!is_callable('smarty_mb_to_unicode')) {
+                    require_once(SMARTY_PLUGINS_DIR . 'shared.mb_unicode.php');
+                }
                 foreach (smarty_mb_to_unicode($string, Smarty::$_CHARSET) as $unicode) {
                     if ($unicode >= 126) {
                         $return .= '&#' . $unicode . ';';
diff --git a/libs/plugins/modifier.replace.php b/libs/plugins/modifier.replace.php
index aa5e8570..9dca259d 100644
--- a/libs/plugins/modifier.replace.php
+++ b/libs/plugins/modifier.replace.php
@@ -25,8 +25,9 @@
 function smarty_modifier_replace($string, $search, $replace)
 {
     if (Smarty::$_MBSTRING) {
-        require_once(SMARTY_PLUGINS_DIR . 'shared.mb_str_replace.php');
-
+        if (!is_callable('smarty_mb_str_replace')) {
+            require_once(SMARTY_PLUGINS_DIR . 'shared.mb_str_replace.php');
+        }
         return smarty_mb_str_replace($search, $replace, $string);
     }
 
diff --git a/libs/plugins/modifiercompiler.escape.php b/libs/plugins/modifiercompiler.escape.php
index 48161066..11565c2d 100644
--- a/libs/plugins/modifiercompiler.escape.php
+++ b/libs/plugins/modifiercompiler.escape.php
@@ -6,11 +6,6 @@
  * @subpackage PluginsModifierCompiler
  */
 
-/**
- * @ignore
- */
-require_once(SMARTY_PLUGINS_DIR . 'shared.literal_compiler_param.php');
-
 /**
  * Smarty escape modifier plugin
  * Type:     modifier<br>
@@ -28,6 +23,9 @@ require_once(SMARTY_PLUGINS_DIR . 'shared.literal_compiler_param.php');
 function smarty_modifiercompiler_escape($params, $compiler)
 {
     static $_double_encode = null;
+    if (!is_callable('smarty_literal_compiler_param')) {
+        require_once(SMARTY_PLUGINS_DIR . 'shared.literal_compiler_param.php');
+    }
     if ($_double_encode === null) {
         $_double_encode = version_compare(PHP_VERSION, '5.2.3', '>=');
     }