[PHP] Revisit cliCalled and runStreamCalled binary flags in the PHP class

[adamziel]

		if (this.cliCalled) {
			throw new Error(
				'php.cli() can only be called once. The method sets a C-level global state that does not allow repeated calls.'
			);
		}
		if (this.runStreamCalled) {
			throw new Error(
				'php.cli() can only be called if php.runStream() was not called before. The two methods set a conflicting ' +
					'C-level global state.'
			);
		}

PR #2281 added php.cliCalled and php.runStreamCalled flags to prevent calling the mutually incompatible cli() and run() methods on the same PHP instance.

@brandonpayton noted:

My intuition feels cautious about keeping these kinds of binary usage flags, and I am trying to determine why.

Instead of tracking whether an instance was used in a way that may conflict, would there be any benefit to explicitly modeling the relationship that callers may have with a PHP instance? Specifically, if calling cli() renders a PHP instance unusable for further requests, what if there is no cli() instance method but rather a standalone function or static method for one-time CLI execution?

Then AFAICT there would be no possibility of callers doing conflicting things with a PHP instance.

I've replied:

I like that direction! I'm trying to think of a specific way of using such an API, e.g. nothing prevents me from doing something like cli(php, args); php.run();. I wonder if we could handle it at a level higher than the PHP instance, e.g. with a method such as acquireForCLI() where reap() would destroy the php instance instead of allowing the system to recycle it.

One other thought I had was having a separate class PHPCLI that only has a .cli() method. That would complicate the types across workers, though.

Perhaps the best solution would be to just rotate the PHP runtime within the PHP class every time we call .cli().