[Sync-En] SplFixedArray: non-integer key throws TypeError as of PHP 8.1.0 - #1133

structure differs from doc-en (EN: xi:include(xpointer=xmlns(db=http://docbook.org/ns/docbook) xpointer(id('class.splfixedarray')/db:refentry/db:refsect1[@ROLE='description']/descendant::db:methodsynopsis[@ROLE='SplFixedArray'])) | translation: xi:fallback) [blocks EN=49 translation=51]