This is a problem in PHP, which has both primitives (including copy-on-write arrays) and Java-style objects, but it also has literal pass-by-reference referenci

This is a problem in PHP, which has both primitives (including copy-on-write arrays) and Java-style objects, but it also has literal pass-by-reference referencing (you can write a swap function). The misuse of “pass-by-reference” here creates confusion.