We know a lot about arrays already. Now, we are going to shift our focus to a new type of data structure known as a list. It is one of the most used data structures in the programming world. In most of the programming languages, the array is a fixed size structure. As a result, it cannot grow dynamically, and shrinking or removing an item from a fixed size array is also problematic since we have to shift the array's items to fill up the gap. For this reason, many developers prefer lists instead of arrays. Considering the fact that each array element can have an overhead of some extra bytes, linked lists can be used where memory efficiency is a big factor. In this chapter, we will explore the different types of linked lists in PHP and their implementation. We will also look at real-world problems that can be solved using linked lists.