Fix bug 81159

[Girgias]

Found partly when looking at #6106 again, but out handling of offsets is really a mess as the handling of Object (namely SPL), strings, and arrays all depend of their context which are all probably deserving of their own bug reports.

[nikic]

The first commit looks good.

For the second commit, if we want to make this change, I should it should happen in a more principled way, by reusing the zend_check_string_offset() logic. Now you're handling one of the error cases, but for example not the warning that occurs for float null/true/false/float offsets.

[Girgias]

The first commit looks good.

The GC assertion on MacOS seems to be related to that one tho

For the second commit, if we want to make this change, I should it should happen in a more principled way, by reusing the zend_check_string_offset() logic. Now you're handling one of the error cases, but for example not the warning that occurs for float null/true/false/float offsets.

Right, that's actually a good idea, should also fix the leading numeric string issue.

[nikic]

The first might be a candidate for PHP-8.0, but I don't think the second one should go on a release branch.

[nikic]

LG if CI happy.