Optimization idea: optimize str_{starts|ends}_wtih() with a 1 byte needle string to $haystack[{0|-1}] === $needle

[Girgias]

Description

Thought about when seeing the following post: https://phpc.social/@linc/117163847782802693

[TimWolla]

I thought about this before, but it's not entirely trivial: Accessing offsets on an empty string emits a warning. And $haystack needs to be type-checked and possibly coerced to string.

[Girgias]

The optimizer should be able to enfer if $haystack is always a string, I guess we don't try to track if a string is possible empty like we do for arrays with MAY_BE_ARRAY_EMPTY.

Which I one could try to add an extra strlen($haystack) != 0 check otherwise.