Welcome to an exciting exploration of two fundamental data structures: Stacks and Queues in PHP! In computing, these structures help organize data efficiently. Stacks and Queues are akin to stacking plates and standing in a line, respectively. For queues, we will use PHP's SplQueue, and for stacks, we will utilize a simple array, though SplStack is also an option, as we'll mention later.

A Stack adheres to the "Last In, First Out" or LIFO principle. It's similar to a pile of plates where the last plate added is the first one to be removed. In this section, we will use a simple array to implement a stack. The primary operations for stacks involve adding and removing elements:

• push: Adds an element to the top of the stack.
• pop: Removes the top element from the stack.
• isEmpty: Checks whether the stack is empty.
• top: Returns the top element of the stack without removing it.

Let's explore this concept using a pile of plates as an analogy.