UPDATE: Apple has announced the iPhone XS and XS Max with dual-SIM support. Check out What is an eSIM and what does it mean for your new iPhone XS or XS Max?
Original story continues below...
It looks like Apple is working on dual-SIM support for future iPhones.
The evidence was uncovered by 9to5Mac within the iOS 12 beta 5 code - there are references to "second SIM status", "dual SIM device" and "second SIM tray status".
That last one is interesting because it could hint that it definitely means there would be two physical SIM slots rather than one physical card and an e-SIM.
Because of space-saving, it's likely that Apple would favour e-SIM technology if it had a choice as it does with the Apple Watch Series 3.
Dual-SIMs are still pretty popular in many countries - although not in the USA and Europe - and it would certainly give a cheaper Apple handset some added appeal. It's also of use for travellers who regularly go between two countries.
If dual-SIM slots do appear in an iPhone it's likely to be a cheaper model. And it's rumoured that there will be three iPhones this year including a cheaper Face ID model.
However, it may be that dual-SIMs will instead appear in the much-talked about iPhone SE replacement which surely must be coming.