MattDees/pear-core — comment on commit 6151eae601524b1dd6faca117d9603b7f3fd6651
File:  line 0
By CloCkWeRX:

So... I imagine this might avoid the problem a bit, but it makes dirname($descfile) the place things are written. That's not exactly the intent of the code.
Are you able to see where it's instantiating something that isn't a PEAR_PackageFile_v1 or explain that a bit better? I imagine that only "PEAR_PackageFile_v2" is the other alternative that is pushed through there... but it's its false/null/etc then it indicates a different problem.