Looks good. I have a couple of questions and comments:
1.) Your license blocks still have <ORGANIZATION> in them. Should be set to you or your company.
2.) Consider the subject-observer pattern for logging rather than providing an empty log method. See http://www.php.net/manual/en/class.splsubject.php
3.) What legitimate uses does this have? The code says right in it "Mining PageRank is AGAINST GOOGLE'S TERMS OF SERVICE. Yes, I'm talking to you, scammer." You should outline the legitimate uses in the package description and make it clear what the illegitimate uses are.