Mark Baker made some fascinating benchmarks on the performance of PHP 7's anonymous classes.

A week or so ago, I published an article entitled “In Search of an Anonymous Class Factory” about my efforts at writing a “factory” for PHP7’s new Anonymous Classes (extending a named concrete base class, and assigning Traits to it dynamically); and about how I subsequently discovered the expensive memory demands of my original factory code, and then rewrote it using a different and (hopefully) more memory-efficient approach. Since then, I’ve run some tests for memory usage and timings to assess just how inefficient my first attempt at the factory code was, and whether the new version of the factory really was better than the original.

https://markbakeruk.net/2016/05/12/anonymous-class-factory-the-results-are-in/