Article claims python 3 uses UTF-8.

https://stackoverflow.com/questions/1838170/ "In Python 3.3 and above, the internal representation of the string will depend on the string, and can be any of latin-1, UCS-2 or UCS-4, as described in PEP 393."

Article also says PHP has immutable strings. They are mutable, although often copied.

Article also claims majority of popular languages have immutable strings. As well as the ones listed there is also PHP and Rust (and C, but they did say C++).

Important information omitted from title: this is for the Ruby language.