The PHP Standard PHP Library (SPL) has an implementation of a doubly linked list, which is known as SplDoublyLinkedList. If we are using the built-in class, we do not need to implement the doubly linked list ourselves. The doubly linked list implementation actually works as a stack and queue as well. The PHP implementation of the doubly linked list has lots of additional functionalities. Here are some of the common features of SplDoublyLinkedList:
|
Method |
Description |
|
Add |
Adds a new node in a specified index |
|
Bottom |
Peeks a node from beginning of the list |
|
Count |
Returns the size of the list |
|
Current |
Returns the current node |
|
getIteratorMode |
Returns the mode of iteration |
|
setIteratorMode |
Sets the mode of iteration. For example, LIFO, FIFO, and so on |
|
Key |
Returns the current node index |
|
next |
Moves to the next node |
|
pop |
Pops a node from the end of the list |
|
prev |
Moves to the previous node |
|
push |
Adds a new node at the end of the list |
|
rewind |
Rewinds the iterator back to the top |
|
shift |
Shifts a node from the beginning of the linked list |
|
top |
Peeks a node from the end of the list |
|
unshift |
Prepends an element in the list |
|
valid |
Checks whether there are any more nodes in the list |
Now, let's write a small program using SplDoublyLinkedList for our book titles applications:
$BookTitles = new SplDoublyLinkedList();
$BookTitles->push("Introduction to Algorithm");
$BookTitles->push("Introduction to PHP and Data structures");
$BookTitles->push("Programming Intelligence");
$BookTitles->push("Mediawiki Administrative tutorial guide");
$BookTitles->add(1,"Introduction to Calculus");
$BookTitles->add(3,"Introduction to Graph Theory");
for($BookTitles->rewind();$BookTitles->valid();$BookTitles->next()){
echo $BookTitles->current()." ";
}
The preceding code will have the following output:
Introduction to Algorithm
Introduction to Calculus
Introduction to PHP and Data structures
Introduction to Graph Theory
Programming Intelligence
Mediawiki Administrative tutorial guide