The most common question from students who is learning website hacking techniques is "how to test my skills legally without getting into troubles?".  So, i always suggest them to use some vulnerable web application such as DVWA. 

However, i felt dvwa is not suitable for new and advanced techniques.  Mutillidae is one of the best web application vulnerable app to date. However, I missed some techniques/features in Mutillidae.  so i thought it is better develop our own app to teach the web application pentesting for my readers and students. 

BTS PenTesting Lab is a vulnerable web application that allows you to learn from basic to advanced  vulnerability techniques.