PHP 7.0.6 Released

    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

    User Contributed Notes

    Gilles A
    2 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
    Maaz Rehman
    11 months 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/>";;
        }
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