The IBM developerWorks site has a new tutorial posted talking about how PHP has been "renewed" in recent versions, more specifically in the password security department.
When PHP was first crafted in the mid-1990s, the term web application didn't even exist yet. Password protection, then, wasn't one of the features that the PHP creators devoted resources to. After all, you didn't need to worry about passwords when you used PHP just to put a site-visit counter or a date-modified stamp on your web page. But 20 years have passed, and now it's almost unthinkable to create a web application that doesn't involve password-protected user accounts. It's of the utmost importance that PHP programmers safeguard account passwords by using the latest and most secure methods.
The article goes on to talk about the importance of using secure hashing methods for password storage, the speed at which "cracking" programs can run and the use of "rainbow tables". It then gets into some of the older methods commonly used for password storage and protection and shows how to refactor them into the new password hashing functionality introduced in PHP 5.5.