device detection in opera mini and opera mobile

i use $_SERVER['HTTP_USER_AGENT'] for detecting mobile device model .but only some browsers are returns device name and model number like uc web and nokia in built browser.opera mini does not returns the device name and model no.then i use $_SERVER['HTTP_X_OPERAMINI_PHONE_UA']. this returns the value UNTRUSTED/1.0.how to resolve this value