Never* use arrays
PHP loves its arrays. Arrays are the uber-data structure. They're a list, a map, a stack, a queue, everything in one! Which is the problem.
Modern PHP grossly over-uses arrays. In most cases there are better options today, and when you find yourself reaching for "oh I'll just make this an associative array", stop. An extra 60 seconds of thought and code will often give you a more readable, faster, more memory-efficient, more flexible alternative. Classes, iterables, and collections can and should replace arrays in most of your day to day coding.
