As is mentioned in this quick post Codecourse (formerly PHP Academy) has posted a series of free videos to YouTube that aim to help you increase the security of your PHP applications. These videos go beyond the usual OWASP Top 10 you'll see in most security-related resources and dive into both some "old favorites" and some new interesting topics.
This YouTube series from Codecourse gives you a good overview of the most common PHP security issues. They use a very practical approach, showing how the attacks are done and how to protect your code from them.
Topics covered in the video series include things like:
There's ten videos in the series with a total run time of about an hour. They're split up for great bite-sized viewing chunks, so be sure to check them all out and see what you can learn.