diff --git a/system/helpers/security_helper.php b/system/helpers/security_helper.php
index 97c9a6b..7552fd8 100644
--- a/system/helpers/security_helper.php
+++ b/system/helpers/security_helper.php
@@ -35,10 +35,13 @@
  * @param	string	the character set of your data
  * @return	string
  */	
-function xss_clean($str, $charset = 'ISO-8859-1')
+if (! function_exists('xss_clean'))
 {
-	$CI =& get_instance();
-	return $CI->input->xss_clean($str, $charset);
+	function xss_clean($str, $charset = 'ISO-8859-1')
+	{
+		$CI =& get_instance();
+		return $CI->input->xss_clean($str, $charset);
+	}
 }
 
 // --------------------------------------------------------------------
@@ -49,32 +52,35 @@
  * @access	public
  * @param	string
  * @return	string
- */		
-function dohash($str, $type = 'sha1')
-{
-	if ($type == 'sha1')
+ */	
+if (! function_exists('dohash'))
+{	
+	function dohash($str, $type = 'sha1')
 	{
-		if ( ! function_exists('sha1'))
+		if ($type == 'sha1')
 		{
-			if ( ! function_exists('mhash'))
-			{	
-				require_once(BASEPATH.'libraries/Sha1'.EXT);
-				$SH = new CI_SHA;
-				return $SH->generate($str);
+			if ( ! function_exists('sha1'))
+			{
+				if ( ! function_exists('mhash'))
+				{	
+					require_once(BASEPATH.'libraries/Sha1'.EXT);
+					$SH = new CI_SHA;
+					return $SH->generate($str);
+				}
+				else
+				{
+					return bin2hex(mhash(MHASH_SHA1, $str));
+				}
 			}
 			else
 			{
-				return bin2hex(mhash(MHASH_SHA1, $str));
-			}
+				return sha1($str);
+			}	
 		}
 		else
 		{
-			return sha1($str);
-		}	
-	}
-	else
-	{
-		return md5($str);
+			return md5($str);
+		}
 	}
 }
 	
@@ -87,12 +93,15 @@
  * @param	string
  * @return	string
  */	
-function strip_image_tags($str)
+if (! function_exists('strip_image_tags'))
 {
-	$str = preg_replace("#<img\s+.*?src\s*=\s*[\"'](.+?)[\"'].*?\>#", "\\1", $str);
-	$str = preg_replace("#<img\s+.*?src\s*=\s*(.+?).*?\>#", "\\1", $str);
+	function strip_image_tags($str)
+	{
+		$str = preg_replace("#<img\s+.*?src\s*=\s*[\"'](.+?)[\"'].*?\>#", "\\1", $str);
+		$str = preg_replace("#<img\s+.*?src\s*=\s*(.+?).*?\>#", "\\1", $str);
 			
-	return $str;
+		return $str;
+	}
 }
 	
 // ------------------------------------------------------------------------
@@ -104,9 +113,12 @@
  * @param	string
  * @return	string
  */	
-function encode_php_tags($str)
+if (! function_exists('encode_php_tags'))
 {
-	return str_replace(array('<?php', '<?PHP', '<?', '?>'),  array('&lt;?php', '&lt;?PHP', '&lt;?', '?&gt;'), $str);
+	function encode_php_tags($str)
+	{
+		return str_replace(array('<?php', '<?PHP', '<?', '?>'),  array('&lt;?php', '&lt;?PHP', '&lt;?', '?&gt;'), $str);
+	}
 }
 
 ?>
\ No newline at end of file