Search engine does not divulge their ranking process. Their process is often referring to as the “Ranking algorithm†which is a fancy math term for a series of calculations that takes place using a set of rules.
PageRank is a link analysis algorithm that assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web, with the purpose of “measuring†its relative importance within the set.
PR hardly matters.. it comes with time.. focus on SERP which is responsible for generating more traffic to your site...