Just use an IDE. phpStorm pretty much does this already.
If creating classes is a serious bottleneck in your app, you need to create fewer classes.
Let's assume this saves you ~15 seconds per class (which I think is generous). Let's also say you're creating a project with 100 classes (way too many -- use external libs instead).
Those 1,500 seconds add up to 25 minutes. Hardly a big deal for a project that's so big, you think it requires 100 brand new classes.
The personality of a programmer is to despise simple repetition that can easily be turned into code. This unfortunately often leads to micro-optimizations and tools that take longer to build than to solve a problem.
