Priority Queues in PHP - php

Question

I'm trying to create a priority queue using this code and I can't find where the problem is. Someone tell me where I went wrong.
<?php
class PriorityQueue implements Iterator , Countable
{
public function __construct() {
$flags = self::EXTR_DATA;
$items = array();
}
function compare ( mixed $priority1 , mixed $priority2 ){}
function count (){
return count($this->items);
}
function current (){
switch ($this->flags) {
case self::EXTR_BOTH:
$ret = array();
$ret['Patient'] = current($this->items);
$ret['Priority'] = $this->key();
break;
case self::EXTR_DATA:
$ret = current($this->items);
break;
case self::EXTR_PRIORITY:
$ret = $this->key();
break;
};
return $ret;
}
function extract (){
$ret = $this->current();
$this->next();
return $ret;
}
function insert ($name,$priority){
$patient = array();
return $patient[$name] = $priority;
}
function isEmpty ()
{
return empty($this->items);
}
function key (){
return substr(key($this->items), 0, 9);
}
function next (){
//array_shift($this->items);
return($this->items);
echo "<br />";
}
function recoverFromCorruption (){}
function rewind (){}
function setExtractFlags (int $flags ){
switch ($flags) {
case self::EXTR_BOTH:
case self::EXTR_DATA:
case self::EXTR_PRIORITY:
$this->flags = $flags;
break;
};
}
function top (){
return $this->current();
}
function valid () {
if (NULL !== key($this->items)) {
return TRUE;
}
return FALSE;
}// function valid
/**
* Extract the data.
*/
const EXTR_DATA = 1;
/**
* Extract the priority.
*/
const EXTR_PRIORITY = 2;
/**
* Extract an array containing both priority and data.
*/
const EXTR_BOTH = 3;
};
$objPQ = new splPriorityqueue();
$objPQ->insert('Richard',9);
$objPQ->insert('paul',1);
$objPQ->insert('Ken',8);
$objPQ->insert('peter',2);
$objPQ->insert('Rick',7);
$objPQ->insert('Dan',5);
echo "PATIENTS = ".$objPQ->count()."<br />";
//mode of extraction
$objPQ->setExtractFlags(splPriorityqueue::EXTR_BOTH);
//Go to TOP
$objPQ->top();
for($i=0,$j=$objPQ->count(); $i<$j; $i++){
//print_r($objPQ->current());
$patients = $objPQ->current();
foreach ($patients as $patient=>$value){
echo $patient."<br />".$value;
$objPQ->next();
echo "<br />";
}
}
?>
I'm now getting some weird result
data-patient Richard
priority-9
......
etc
I want to get results to be
Richard - 9
Ken - 8
Rick - 7
Dan - 5
Peter - 2
Paul - 1
Considering the priority given

Answer 1

The Standard PHP Library (SPL) implements the SplPriorityQueue class :
$pq = new SplPriorityQueue();
// The insert method inserts an element in the queue by shifting it up
$pq->insert('A', 3);
$pq->insert('B', 6);
$pq->insert('C', 1);
$pq->insert('D', 2);
// Count the elements
echo "count ->" . $pq->count() . PHP_EOL;
// Sets the mode of extraction (EXTR_DATA, EXTR_PRIORITY, EXTR_BOTH)
$pq->setExtractFlags(SplPriorityQueue::EXTR_BOTH);
// Go at the node from the top of the queue
$pq->top();
// Iterate the queue (by priority) and display each element
while ($pq->valid()) {
print_r($pq->current());
echo PHP_EOL;
$pq->next();
}

Answer 2

Try this modified class:
class PriorityQueue implements Iterator, Countable {
/**
* Extract the data.
*/
const EXTR_DATA = 1;
/**
* Extract the priority.
*/
const EXTR_PRIORITY = 2;
/**
* Extract an array containing both priority and data.
*/
const EXTR_BOTH = 3;
private $flags;
private $items;
public function __construct() {
$this->flags = self::EXTR_DATA;
$this->items = array();
}
function compare($priority1, $priority2) {}
function count() {
return count($this->items);
}
function extract() {
$result = $this->current();
$this->next();
return $result;
}
function current() {
switch ($this->flags) {
case self::EXTR_BOTH:
$result = $this->key() . ' - ' . current($this->items);
break;
case self::EXTR_DATA:
$result = $this->key();
break;
case self::EXTR_PRIORITY:
$result = current($this->items);
break;
default:
$result = '';
}
return $result;
}
function key() {
return key($this->items);
}
function next() {
return next($this->items);
}
function insert($name, $priority) {
$this->items[$name] = $priority;
asort($this->items);
return $this;
}
function isEmpty() {
return empty($this->items);
}
function recoverFromCorruption() {}
function rewind() {}
function setExtractFlags($flags) {
switch ($flags) {
case self::EXTR_BOTH:
case self::EXTR_DATA:
case self::EXTR_PRIORITY:
$this->flags = $flags;
break;
};
}
function valid() {
return (null === key($this->items)) ? false : true;
}
}
Usage:
$patients = new PriorityQueue();
$patients->setExtractFlags(PriorityQueue::EXTR_BOTH);
$patients->insert('Richard', 9)
->insert('paul', 1)
->insert('Ken', 8)
->insert('peter', 2)
->insert('Rick', 7)
->insert('Dan', 5);
foreach($patients as $patient) {
echo $patient->current();
}