I want upgrade my php version to 5.3.20, but i have a doubt about this upgrade if i'll having a problem with my clients, like some scripts stop to work.
There's any risk to upgrade this php version on production server ?
Yes, there is always an issue that you will encounter script problems. I'd recommend advising your clients before and recommending that they are running the latest version of their scripts before you perform your upgrade so as to ensure maximum compatability
You can review the changes to determine if they will cause any problems with your PHP scripts. Upgrading a minor version of PHP (e.g. 5.3.17 to 5.3.20) does not typically result in any compatibility issues.