I share the same concerns as Rowan Collins, and I'm really not a fan of the RFC in general. Also I think those kind of magic numbers should be constants with meaningful names, and it that case you could just compute them by adding powers of ten. E.g. DISCOUNT_IN_CENTS = 1 * 10^5 + 3 * 10^4 + 5 * 10^3; Now I'm assuming opcache would compile this into a final integer but I may be wrong on how the internals of the engine work in this case. Moreover I feel that people may misread numbers like that if people use different groupings. E.g. 1_0000_0000_0000; by skimming rapidly I could think it's a billion(10^6) when in reality it's a trillion (10^9). Even if maybe some countries are moving away from the grouping digits in groups of 4.
I'll probably vote against it but that's only my opinion. George P. Banyard