azjezz/psl
PSL (PHP Standard Library) offers a consistent, well-typed set of safer, async-ready APIs to replace PHP primitives. Covers async, collections, networking, I/O, cryptography, terminal UI, and type-safe data validation with predictable errors.
The DataStructure component provides three classic data structures: Queue (FIFO), Stack (LIFO), and PriorityQueue. They are generic, type-safe, and offer a consistent API with both safe and throwing access methods.
A queue processes items in first-in, first-out order. Items are added to the back and removed from the front:
@example('collections/data-structure-queue.php')
Use pull() when an empty queue is a normal condition (it returns null). Use dequeue() when an empty queue is a bug (it throws UnderflowException).
A stack processes items in last-in, first-out order. Items are added to and removed from the top:
@example('collections/data-structure-stack.php')
Use pull() for safe access (returns null if empty) and pop() when emptiness is unexpected (throws UnderflowException).
A priority queue dequeues items with the highest priority first. Items with equal priority are dequeued in FIFO order:
@example('collections/data-structure-priority-queue.php')
If no priority is specified, items default to priority 0.
All three structures implement Countable and share a consistent pattern:
| Method | Queue | Stack | PriorityQueue |
|---|---|---|---|
| Add item | enqueue($item) |
push($item) |
enqueue($item, $priority) |
| Peek at next | peek() |
peek() |
peek() |
| Remove (safe) | pull() |
pull() |
pull() |
| Remove (throws) | dequeue() |
pop() |
dequeue() |
| Count items | count() |
count() |
count() |
peek() returns the next item without removing it, or null if emptypull() removes and returns the next item, or null if emptydequeue() / pop() removes and returns the next item, or throws UnderflowException if emptySee src/Psl/DataStructure/ for the full API.
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