PHP SPL Data structures

The Standard PHP Library (SPL) includes common data structures. The SPL groups these structures by how they are implemented.

Here's an example that shows how to use the `SplDoublyLinkedList::offsetGet()` function in PHP:

<?php 
  
// Declare an empty SplDoublyLinkedList 
$list = new \SplDoublyLinkedList; 
  
// Use SplDoublyLinkedList::add() function to 
// add elements to the SplDoublyLinkedList 
$list->add(0, 30); 
$list->add(1, 20); 
$list->add(2, 30); 
$list->add(3, "Geeks"); 
$list->add(4, 'G'); 
$list->rewind(); 
  
// Use SplDoublyLinkedList::offsetGet() function 
// to check index exist or not 
var_dump($list->offsetGet(2)); 
  
var_dump($list->offsetGet(3)); 
  
?>

Output:

int(30)
string(5) "Geeks"

Complete List of PHP SPL SplDoublyLinkedList Functions:

Doubly Linked List Functions	Description
add()	Add a new value at the specified index in the list.
bottom()	Peek at the value of the first node (at the beginning) of the doubly linked list without removing it.
count()	Count the number of elements present in the doubly linked list.
current()	Return the value of the current element pointed to by the internal iterator.
isEmpty()	Check whether the doubly linked list is empty (contains no elements).
key()	Return the index (or key) of the current node pointed to by the internal iterator.
next()	Move the internal iterator to the next node in the list.
offsetExists()	Check whether a specific index exists in the doubly linked list.
offsetGet()	Get the value at the specified index in the doubly linked list.
offsetSet()	Set the value at the specified index in the doubly linked list.
offsetUnset()	Unset (remove) the value at the specified index in the doubly linked list.
pop()	Remove and return the value of the last node (at the end) of the doubly linked list.
prev()	Move the internal iterator to the previous node in the list.
push()	Add a new element to the end of the doubly linked list.
rewind()	Reset the internal iterator to point to the first node (beginning) of the list.
shift()	Remove and return the value of the first node (at the beginning) of the doubly linked list.
top()	Return the value of the last node (at the end) of the doubly linked list without removing it.
unshift()	Add a new element to the beginning of the doubly linked list.

Complete List of PHP SPL SplObjectStorage Functions

SplObjectStorage Functions	Description
addAll()	Add all elements from another storage object to the current SplObjectStorage.
attach()	Add an object to the SplObjectStorage. You can optionally associate data with the object.
contains()	Check whether the storage contains a specific object.
count()	Count the number of objects in the storage.
current()	Get the value associated with the current iterator entry (the object itself).
detach()	Remove an object from the SplObjectStorage.
getInfo()	Get the data associated with the object pointed to by the current iterator.
key()	Get the index (object) of the element pointed to by the current iterator.
next()	Move the internal iterator to the next element in the storage.
offsetExists()	Check whether a specific object exists in the storage.
offsetGet()	Get the data associated with the object at the specified index.
offsetSet()	**Not recommended:** While technically possible, setting an object at a specific index using offsetSet is not recommended for SplObjectStorage. It's better to use `attach()` with the desired object and data.
offsetUnset()	Remove the object and its associated data from the storage at the specified index.
removeAll()	Remove all objects from the current storage that are also contained in another storage.
removeAllExcept()	Remove all objects from the current storage except for those that are also contained in another storage.
rewind()	Reset the internal iterator to point to the first element (beginning) of the storage.
serialize()	Serialize the SplObjectStorage object to a string representation.
setInfo()	Set the data associated with the current iterator entry (the object itself).
unserialize()	Unserialize a SplObjectStorage object from a previously serialized string.
valid()	Check whether the current iterator is pointing to a valid element in the storage (i.e., not "past the end").

Complete List of PHP SPL SplQueue Functions:

Queue Functions	Description
__construct()	Optional: Initializes a queue object. In some implementations, a queue can be created without explicitly calling a constructor.
dequeue()	Remove and return the element from the front (beginning) of the queue. If the queue is empty, it may return an error or null value.
enqueue()	Add a new element to the back (end) of the queue.