Are you sure? The bug you reference dates to 2004 and is related to MySQL?
Anyway, if you have a problem with a php bug, you most likely need to upgrade to a newer version that has the bug fixed. For Linux, php is not provided by Plesk - it comes from your Linux OS, so you would upgrade it like any other OS component (e.g. for RedHat/Centos etc) "yum list upgrades" to see what needs updating and "yum upgrade php" to upgrade php if it does etc etc. Please be careful if you are unfamiliar with any of this -- you can potentially mess up your system.