Added ->db->replace() for MySQLi.
diff --git a/system/database/drivers/mysqli/mysqli_driver.php b/system/database/drivers/mysqli/mysqli_driver.php
index 4af08c8..fb5953b 100644
--- a/system/database/drivers/mysqli/mysqli_driver.php
+++ b/system/database/drivers/mysqli/mysqli_driver.php
@@ -574,6 +574,25 @@
 
 	// --------------------------------------------------------------------
 
+
+	/**
+	 * Replace statement
+	 *
+	 * Generates a platform-specific replace string from the supplied data
+	 *
+	 * @access	public
+	 * @param	string	the table name
+	 * @param	array	the insert keys
+	 * @param	array	the insert values
+	 * @return	string
+	 */
+	function _replace($table, $keys, $values)
+	{
+		return "REPLACE INTO ".$table." (".implode(', ', $keys).") VALUES (".implode(', ', $values).")";
+	}
+	
+	// --------------------------------------------------------------------
+
 	/**
 	 * Update statement
 	 *