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The SplDoublyLinkedList class

(PHP 5 >= 5.3.0, PHP 7)

Introduction

The SplDoublyLinkedList class provides the main functionalities of a doubly linked list.

Class synopsis

SplDoublyLinkedList implements Iterator , ArrayAccess , Countable {
/* Methods */
public __construct ( void )
public void add ( mixed $index , mixed $newval )
public mixed bottom ( void )
public int count ( void )
public mixed current ( void )
public int getIteratorMode ( void )
public bool isEmpty ( void )
public mixed key ( void )
public void next ( void )
public bool offsetExists ( mixed $index )
public mixed offsetGet ( mixed $index )
public void offsetSet ( mixed $index , mixed $newval )
public void offsetUnset ( mixed $index )
public mixed pop ( void )
public void prev ( void )
public void push ( mixed $value )
public void rewind ( void )
public string serialize ( void )
public void setIteratorMode ( int $mode )
public mixed shift ( void )
public mixed top ( void )
public void unserialize ( string $serialized )
public void unshift ( mixed $value )
public bool valid ( void )
}

Table of Contents

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User Contributed Notes 4 notes

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24
Maaz Rehman
2 years ago
/*
php doubly link list is an amazing data structure ,doubly means you can traverse forward as well as backward, it can act as a deque(double ended queue) if you want it to,
here is how it works

*/

//instantiating an object of doubly link list

$dlist=new SplDoublyLinkedList();

//a push inserts data at the end of the list
$dlist->push('hiramariam');
$dlist->push('maaz');
$dlist->push('zafar');

/* the list contains
hiramariam
maaz
zafar
*/

//while an unshift inserts an object at top of the list
$dlist->unshift(1);
$dlist->unshift(2);
$dlist->unshift(3);

/* the list now contains
3
2
1
hiramariam
maaz
zafar
*/

//you can delete an item from the bottom of the list by using pop
$dlist->pop();

/* the list now contains
3
2
1
hiramariam
maaz

*/
//you can delete an item from the top of the list by using shift()
$dlist->shift();

/* the list now contains

2
1
hiramariam
maaz

*/

/* if you want to replace an item at particular index you can use a method named add , note that if you want to replace an item that does not exist , an exception will be thrown*/

$dlist->add(3 , 2.24);

/*
to go through the list we use a simple for loop, the rewind() method shown below point to the initials of the list depending on the iterator, a valid() method checks whether a list is still valid or not , meaning it ensures the loop does not go on and on after we reach the last data in the list , and the next() method simply points to the next data in the list.

*/
for($dlist->rewind();$dlist->valid();$dlist->next()){
   
    echo $dlist->current()."<br/>";
    }
echo "<br/>";
/*

To traverse backward

*/
$dlist->setIteratorMode(SplDoublyLinkedList::IT_MODE_LIFO);
for($dlist->rewind();$dlist->valid();$dlist->next()){
   
    echo $dlist->current()."<br/>";;
    }
up
29
Gilles A
4 years ago
FIFO and LIFO in SplDoublyLinkedList

$list = new SplDoublyLinkedList();
$list->push('a');
$list->push('b');
$list->push('c');
$list->push('d');

echo "FIFO (First In First Out) :\n";
$list->setIteratorMode(SplDoublyLinkedList::IT_MODE_FIFO);
for ($list->rewind(); $list->valid(); $list->next()) {
    echo $list->current()."\n";
}

Result :

// FIFO (First In First Out):
// a
// b
// c
// d

echo "LIFO (Last In First Out) :\n";
$list->setIteratorMode(SplDoublyLinkedList::IT_MODE_LIFO);
for ($list->rewind(); $list->valid(); $list->next()) {
    echo $list->current()."\n";
}

Result :

// LIFO (Last In First Out):
// d
// c
// b
// a
up
1
lincoln dot du dot j at gmail dot com
4 months ago
$a = new SplDoublyLinkedList;
$arr=[1,2,3,4,5,6,7,8,9];
for($i=0;$i<count($arr);$i++){
    $a->add($i,$arr[$i]);
}

$a->push(11); //push method
$a->add(10,12); //add method must with index
$a->shift(); //remove array first value
$a->unshift(1); //add first value

$a->rewind(); //initial from first

echo "SplDoublyLinkedList array last/top value " .  $a->top() ." \n";
echo "SplDoublyLinkedList array count value " .  $a->count() ." \n";
echo "SplDoublyLinkedList array first/top value " . $a->bottom() . " \n\n";

while($a->valid()){ //check with valid method
    echo 'key ', $a->key(), ' value ', $a->current(),"\n"; //key and current method use here
    $a->next(); //next method use here
}

$a->pop(); //remove array last value
print_r($a);
$s=$a->serialize();
echo $s;

//Output
SplDoublyLinkedList array last/top value 12
SplDoublyLinkedList array count value 11
SplDoublyLinkedList array first/top value 1

key 0 value 1
key 1 value 2
key 2 value 3
key 3 value 4
key 4 value 5
key 5 value 6
key 6 value 7
key 7 value 8
key 8 value 9
key 9 value 11
key 10 value 12
SplDoublyLinkedList Object
(
    [flags:SplDoublyLinkedList:private] => 0
    [dllist:SplDoublyLinkedList:private] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
            [4] => 5
            [5] => 6
            [6] => 7
            [7] => 8
            [8] => 9
            [9] => 11
        )

)
i:0;:i:1;:i:2;:i:3;:i:4;:i:5;:i:6;:i:7;:i:8;:i:9;:i:11;
up
1
dongchao769390531 at 163 dot com
5 months ago
<?php
$splDoubleLinkedList
= new SplDoublyLinkedList();
$splDoubleLinkedList->push('a');
$splDoubleLinkedList->push('3');
$splDoubleLinkedList->push('v');
$splDoubleLinkedList->push('1');
$splDoubleLinkedList->push('p');
//First of all, we need rewind list
$splDoubleLinkedList->rewind();
//Use while, check if the list has valid node
while ($splDoubleLinkedList->valid()){
   
//Print current node's value
   
echo $splDoubleLinkedList->current()."\n";
   
//Turn the cursor to next node
   
$splDoubleLinkedList->next();
}
?>
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