diff --git a/framework/helper.class.php b/framework/helper.class.php
index b5fbfd6533..300d328578 100644
--- a/framework/helper.class.php
+++ b/framework/helper.class.php
@@ -233,6 +233,47 @@ class helper
         return base64_decode(strtr($string, '.', '/'));
     }
 
+    /**
+     * Judge a string is utf-8 or not.
+     * 
+     * @param  string    $string 
+     * @author hmdker@gmail.com
+     * @see    http://php.net/manual/en/function.mb-detect-encoding.php
+     * @static
+     * @access public
+     * @return bool
+     */
+    static public function isUTF8($string)
+    {
+        $c    = 0; 
+        $b    = 0;
+        $bits = 0;
+        $len  = strlen($string);
+        for($i=0; $i<$len; $i++)
+        {
+            $c = ord($str[$i]);
+            if($c > 128)
+            {
+                if(($c >= 254)) return false;
+                elseif($c >= 252) $bits=6;
+                elseif($c >= 248) $bits=5;
+                elseif($c >= 240) $bits=4;
+                elseif($c >= 224) $bits=3;
+                elseif($c >= 192) $bits=2;
+                else return false;
+                if(($i+$bits) > $len) return false;
+                while($bits > 1)
+                {
+                    $i++;
+                    $b=ord($str[$i]);
+                    if($b < 128 || $b > 191) return false;
+                    $bits--;
+                }
+            }
+        }
+        return true;
+    }
+
     /**
      *  Compute the diff days of two date.
      *