PHP7 was a huge performance leap over 5.x, I saw all the benchmarks and they looked impressive (100% performance, 50-80% reduction in memory usage) and expected

PHP7 was a huge performance leap over 5.x, I saw all the benchmarks and they looked impressive (100% performance, 50-80% reduction in memory usage) and expected the usual "Ok but in the real world I'll get maybe 10-20% because benchmarks" and nope, in production I see exactly what the 5 vs 7 benchmarks show. The memory reductions when dealing with large arrays (pretty much the only datatype in PHP...) are colossal.