In Stephan's post:
Porting JavaDoc comments to PHP was one of the best things, that ever happened to to PHP4. But like in Java 4, the DocBlocks in PHP evolved from plain documentation to a feature that adds meta information to classes, methods, properties and variables. IDEs, like Zend Studio, use the @var tag to enable type hinting for method return values, which would not possible without the DocBlock, as PHP is a dynamic languages.
And from Frank:
In part three of his wishlist for PHP 6 Stephan wrote that he would like to see annotations built into PHP 6 directly. I disagree with him about that. Annotations can be done in userland, without any problems. He already gave some examples of projects that accomplished this task. But if you look at them you see that every project has a different solution on how to implement annotations for PHP which leads to the problem that if you use different projects in your own application you have to handle all their ways of treating annotations. Annoying, isn't it?