and people wonder why we say PHP is a meme

Ah, I understand now. The expression is evaluated like this:

• $a == 1 ? "one" : $a == 2 ? "two" : $a == 3 ? "three" : "other"
• $a == 2 ? "two" : $a == 3 ? "three" : "other"
• "two" ? "three" : "other"
• "three"

If you think PHP is weird, go look up ZZT-OOP, the scripting language from Tim Sweeney's first game.

(No, a scripting language for game characters doesn't need integers. If you need to count, you can do that by moving blocks around on the game board. It's halfway between LOGO and Minecraft.)