ASCII is so 1963. Nowadays, computers must support a broad range of different characters beyond the 128 we had in the early days of computing - not just accents and emojis but also completely different writing systems used around the globe. The Unicode standard packs a whopping 143,859 characters into an elegant system used by over 95% of the Internet, but PHP's string functions don't play nicely with Unicode by default, making it difficult for developers to properly handle such a wide array of possible user inputs.