The data can be deleted by selecting the data and then clicking the delete button or simply setting the device to your factory settings, in this way the data are deleted from the phone. By deleting the data in the above mentioned ways, the data are not deleted permanently, as they can be recovered with the help of any recovery software. And if you want to deleted the data permanently, then with the help of Safe Eraser for iOS, you would be able to delete any data like photos, videos, contacts, messages etc. permanently and once they are deleted with this software, it cannot be recovered by any recovery tool. For more details visit:
http://www.iosdevicerecovery.info/safeeraser-ios.php