This document is targeted at PHP developers writing packages for submission into the PEAR repository. As any coding guidelines, it is useful to developers using PHP in other environments. The requirements for reading this text are only familiarity with PHP as a programming language, as well as familiarity with the mechanism of Exceptions as an error handling mechanism.
For those PHP developers unfamiliar with Exceptions, the wiki page from which this document was extracted provides a good introduction, as well as pointers to other references.