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.

<?php

class StackOfPlates {
    private array $stack;

    public function __construct() {
        $this->stack = array();
    }

    // Inserts a plate at the top of the stack
    public function addPlate(mixed $plate): void {
        array_push($this->stack, $plate); // Using array_push to add a plate
    }

    // Removes the top plate from the stack
    public function removePlate(): mixed {
        if (empty($this->stack)) { // Using isEmpty to check if stack is empty
            return "No plates left to remove!";
        }
        return array_pop($this->stack); // Using array_pop to remove and return the top plate
    }

    public function isEmpty(): bool {
        return empty($this->stack);
    }

    public function top(): mixed {
        if (empty($this->stack)) {
            return "No plates in the stack!";
        }
        return end($this->stack); // Using end to get the top element
    }    
}

// Example usage:
$plates = new StackOfPlates();
$plates->addPlate("Plate");
$plates->addPlate("Another Plate");

echo "Removed: " . $plates->removePlate() . "\n"; // Outputs: Removed: Another Plate

?>

The last plate added was removed first, demonstrating the LIFO property of a stack. While we used an array here for illustration, PHP's Standard PHP Library contains the SplStack class that can also be used for stack operations, providing more functionality and consistency.