PHP - Ds\PriorityQueue::__construct() Function

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The PHP Ds\PriorityQueue::__construct() function is a built-in function which is used to create a new instance or Priority Queue. This function does not accept any argument and also it does not return any value.

Syntax

Below is the syntax of the PHP Ds\PriorityQueue::__construct() function −

public Ds\PriorityQueue::__construct( void )

Parameters

This function does not take any parameters.

Return Value

This function does not return a value. It initializes a new instance of a Ds\PriorityQueue object.

PHP Version

The __construct() function is available from version 1.0.0 of the Ds extension onwards.

Example 1

Here is the basic example of the PHP Ds\PriorityQueue::__construct() function to create a new PriorityQueue.

<?php
   // Create a new instance of PriorityQueue
   $pqueue = new \Ds\PriorityQueue();

   // Output the structure and contents of the PriorityQueue
   var_dump($pqueue);
?>

Output

Here is the outcome of the following code −

object(Ds\PriorityQueue)#1 (0) {
}

Example 2

In the below PHP code we will use the __construct() function and create a simple priority queue and add elements in it.

<?php
   // Create a new instance of PriorityQueue
   $queue = new \Ds\PriorityQueue();

   // Insert the elements in queue
   $queue->push("Task 1", 1); 
   $queue->push("Task 2", 2); 
   $queue->push("Task 3", 3); 
   
   foreach ($queue as $task) {
       echo $task . "\n";
   }
?> 

Output

This will generate the below output −

Task 3
Task 2
Task 1

Example 3

Now the below code, using the __construct() function by adding items that have different priority and keeping track of the order of retrieval.

<?php
   // Create a new instance of PriorityQueue
   $queue = new \Ds\PriorityQueue();

   $queue->push("Low priority task", 1);
   $queue->push("Medium priority task", 5);
   $queue->push("High priority task", 10);
   
   foreach ($queue as $task) {
       echo $task . "\n";
   }
?> 

Output

This will create the below output −

High priority task
Medium priority task
Low priority task

Example 4

In the following example, we are using the __construct() function store objects in the priority queue.

<?php
   // Create a class for task
   class Task {
      public $name;
      public function __construct($name) {
          $this->name = $name;
      }
  }
  
  // Create a new instance of PriorityQueue
  $queue = new \Ds\PriorityQueue();
  
  // Insert the elements in the queue
  $queue->push(new Task("Task A"), 2);
  $queue->push(new Task("Task B"), 1);
  $queue->push(new Task("Task C"), 3);
  
  foreach ($queue as $task) {
      echo $task->name . "\n";
  }
?> 

Output

Following is the output of the above code −

Task C
Task A
Task B

Summary

The Ds\PriorityQueue::__construct() function is a built-in method in PHP which is used to create an instance. And we have demonstrate different examples to show how to create a priority queue, add elements with priorities, and then loop over the queue to get elements based on their priorities.