PHP Multidimensional Arrays: How Many Dimensions Deep Have you Been? What are PHP multidimensional arrays? Just think of an array within an array. In other words, it’s an array that stores arrays as elements. Those elements that are arrays themselves can have arrays as elements. The easiest way to explain this is with some examples. In the previous article on associative arrays, we looked at the $person array. The $person array contains a few key/value pairs such as the person’s name, age, email, occupation, and book_title. The book_title represents the book the author has written. I would assume