void
     HTTP_Download::setData
     ( 
    
     mixed
     
      $data = null
     
    
   )
   Set $data to null if you want to unset.
  
Otherwise you can send any arbitrary data ie. from a database BLOB.
      mixed
      
       $data = null
      
      - any arbietrary data as string to send or null to unset
     
This function can not be called statically.