Step by Step solution about How to resolve the algorithm Queue/Definition step by step in the PHP programming language

The given PHP code defines a simple FIFO (First-In, First-Out) data structure, which is essentially a queue. Let's break down the code step by step to understand how it works:

1. Fifo Class:

   • The code defines a class called Fifo that represents a FIFO queue.

2. Private $data Array:

   • Inside the Fifo class, it declares a private array called $data. This array will be used to store the elements of the queue.

3. push Method:

   • The push method takes an $element as an argument and inserts it into the queue. It uses the array_push function to add the element to the end of the $data array.

4. pop Method:

   • The pop method removes and returns the first element from the queue. It first checks if the queue is empty using the isEmpty method. If the queue is empty, it throws an exception indicating an attempt to pop from an empty queue. Otherwise, it uses array_shift to remove the first element from the $data array and returns it.

5. Alias Functions:

   • The code includes two alias functions:
     • enqueue: This function is an alias for push and simply adds an element to the queue.
     • dequeue: This function is an alias for pop and removes and returns the first element from the queue.

6. isEmpty Method:

   • The isEmpty method checks if the $data array is empty. It returns true if the array is empty and false otherwise.

7. Example Usage:

   • After defining the Fifo class, the code creates an instance of the class named $foo.
   • It then adds elements ('One', 'Two', and 'Three') to the queue using the push method.
   • Finally, it prints the elements from the queue using the pop method. It also demonstrates that attempting to pop from an empty queue will throw an exception.

class Fifo {
  private $data = array();
  public function push($element){
    array_push($this->data, $element);
  }
  public function pop(){
    if ($this->isEmpty()){
      throw new Exception('Attempt to pop from an empty queue');
    }
    return array_shift($this->data);
  }

  //Alias functions
  public function enqueue($element) { $this->push($element); }
  public function dequeue() { return $this->pop(); }

  //Note: PHP prevents a method name of 'empty'
  public function isEmpty(){
    return empty($this->data);
  }
}


$foo = new Fifo();
$foo->push('One');
$foo->enqueue('Two');
$foo->push('Three');

echo $foo->pop();     //Prints 'One'
echo $foo->dequeue(); //Prints 'Two'
echo $foo->pop();     //Prints 'Three'
echo $foo->pop();     //Throws an exception