Detecting browsers current version or better PHP

I am looking for a way to detect whether a user is using certain kinds of browsers on their system. In this example I want to be able to detect:

• IOS 5 or greater for both iPhone or iPAD
• iOS 4 or inferior
• Android
• Safari and Chrome
• Firefox
• Internet Explorer

The only one I know how to create is to detect any version of IE

if(strpos($_SERVER['HTTP_USER_AGENT'], 'iOS 5_0') !== false) { }

So What I need is:

• How to detect browsers
• How to assess whether it is a a certain version newer or older

Someone mentioned before the get_browser functi开发者_StackOverflow社区on but I don't understand who to use this ini file and need a good explanation on how to do it if that is the best approach.