This is not meant to be a slant on PHP but if you're worried about static branch prediction in it, something is probably seriously wrong. Even the most metal-scraping C code often doesn't benefit that much, if any, from it, and the people who focus on that sort of thing are usually zoomed in at the most micro-levels analyzing assembly code and measuring repeatedly with fancy tools to guide their decisions. I wouldn't worry about it even if you want to micro-optimize. It's a bottom priority type of thing even when you're getting really micro with your optimizations.
Focus first and foremost on locality of reference with memory access patterns if you want to go micro. That can make 10x to 100x speed improvements without an improvement to algorithmic complexity. I don't even think it's fair to call them "micro" since something that improves a user-end operaton's speed by 100 times is far from "micro" in impact.
But static branch prediction? You're playing a lottery with that stuff unless you're a complete expert when it comes to assembly, profiling, and computer architecture. I often find any attempts at programming for static branch prediction even in C with VTune in hand for the hottest paths to have negligible effects, even in the tightest loops, and sometimes, counter-intuitively, even negative effects for reasons I don't have sufficient expertise to understand. I hope you don't mind but I'm assuming you also lack such expertise or else this question probably wouldn't be raised, at which point I'd suggest to focus on making your code as easy for you to manipulate as possible without worrying about static branch prediction so that you can prioritize the big stuff like algorithmic improvements, memory access patterns, and parallelism.