Can you tell me which vairable show the screen resolution and operation system of visitor? Another question: I'm thinking to redirect mobile/PDA phone visitor to mobile site. As many latest PDA/phone browsers directly take you to PC site(not wap site), so I want to check it with screen resolution. DO you support the idea ?
HTTP User Agent makes more sense than screen resolution. Keep your browscap.ini file up to date and you'll have what you need.
do you think that in case of using javascript, it will fetch any resolution and even earlier mobile phone wap browser resolution ?
No. Many mobile phones have weird or nonexistent JavaScript implementations. Using JavaScript or making bold and unwarranted assumptions based on screen resolution is a foolish approach. Use $_SERVER['HTTP_USER_AGENT'] or get_browser() and you will get much more accurate information about the type of device you are talking to. It's what they're for.