It's all in the title. PHP is the language I need to fully understand the examples.
Websites? Can't think of any, but these books will help.
There's maybe http://sourcemaking.com/design_patterns though, this has PHP examples.
I wouldn't follow web site blogs or articles, etc. Buy a book from Fowler or even better obtain a copy of the GoF book.
If it is websites you are after, here is some good stuff for starters.
For nailing the real basics on a few patterns I found this IBM site was really useful.
Five common PHP design patterns
This other (coincidentally IBM too) page dealing with basic principles is another I read over quite a few times in conjunction with the above.
Build seven good object-oriented habits in PHP
I get the feeling this site may not be maintained any longer, but is worth looking at because the writing style is good and the examples should chime with you, also, you ought to pick up some Test Driven Design tendencies by association.
Also look at : DevZone - Items tagged as: Design Patterns
I found it useful to study a few basic patterns first, in conjunction with a book or two as Anthony has indicated, before really casting your net wider (GOF, Fowler etc) otherwise you might find it slightly overwhelming and off-putting (well, I did).
You will likely end up buying more that one book, and some of those will contain code examples which use Java and/or C# - but that should not put you off studying them.
These links are from my old bookmarks, but if you purely want libraries of patterns try:
People Projects And Patterns
Design Patterns in Dynamic Programming