That would be very, VERY challenging, as…
a) Apache itself is gross overkill for an embedded platform like a router. The memory and CPU requirements for a LAMP install like you describe are rather heavy (and unnecessarily so). I've found Hiawatha to be a more-than-adequate fill-in that interacts well with PHP, your experience may vary.
b) MySQL is also very, VERY heavy on memory. With anything less than something of the caliber of a RT-N16 and largish USB hard drive (not flash drive), you wouldn't even want to consider such a thing.
Long story short, no guide exists because it's not practical. You _might_ be able to cobble something together that kinda-sorta works with Optware and sufficiently beefy hardware, but in the end it will only be suitable for _very_ light traffic levels at best.
Routers can be made to do unexpectedly useful things, but a full-blown LAMP install is beyond them. =)