Implement stack and queue in PHP

CONTRIBUTORS.md

@@ -64,3 +64,4 @@ This file lists everyone, who contributed to this repo and wanted to show up her
 - K. Shudipto Amin
 - Peanutbutter_Warrior
 - Thijs Raymakers 
+- Abdullah Al Zawad

contents/stacks_and_queues/code/php/queue.php

@@ -0,0 +1,81 @@
+<?php
+
+/**
+ * @template T
+ */
+interface IQueue
+{
+    /**
+     * Removes the first element from the queue and returns it.
+     * @return T | null
+     */
+    public function dequeue();
+
+    /**
+     * Adds an element at the end of the queue and returns the new size.
+     * @param T $element
+     */
+    public function enqueue($element): int;
+
+    /**
+     * Returns the length of the queue.
+     */
+    public function size(): int;
+
+    /**
+     * Returns the first element of the queue.
+     * @return T
+     */
+    public function front();
+}
+
+/**
+ * @template T
+ * @implements IQueue<T>
+ */
+class Queue implements IQueue
+{
+    /**
+     * @var array<T> $elements
+     */
+    private $elements = [];
+
+    public function dequeue()
+    {
+        return array_shift($this->elements);
+    }
+
+    public function enqueue($element): int
+    {
+        array_push($this->elements, $element);
+        return $this->size();
+    }
+
+    public function size(): int
+    {
+        return count($this->elements);
+    }
+
+    public function front()
+    {
+        return $this->elements[0];
+    }
+}
+
+function example_queue(): void
+{
+    /**
+     * @var Queue<int> $int_queue
+     */
+    $int_queue = new Queue();
+
+    $int_queue->enqueue(4);
+    $int_queue->enqueue(5);
+    $int_queue->enqueue(7);
+
+    echo $int_queue->dequeue() . "\n"; // 4
+    echo $int_queue->size() . "\n"; // 2
+    echo $int_queue->front() . "\n"; // 5
+}
+
+example_queue();

contents/stacks_and_queues/code/php/stack.php

@@ -0,0 +1,82 @@
+<?php
+
+/**
+ * @template T
+ */
+interface IStack
+{
+    /**
+     * Removes the last element from the stack and returns it.
+     * @return T | null
+     */
+    public function pop();
+
+    /**
+     * Adds an element at the end of the stack and returns the new size.
+     * @param T $element
+     */
+    public function push($element): int;
+
+    /**
+     * Returns the length of the stack.
+     */
+    public function size(): int;
+
+    /**
+     * Returns the first element of the stack.
+     * @return T
+     */
+    public function top();
+}
+
+/**
+ * @template T
+ * @implements IStack<T>
+ */
+class Stack implements IStack
+{
+    /**
+     * @var array<T> $elements
+     */
+    private $elements = [];
+
+    public function pop()
+    {
+        return array_pop($this->elements);
+    }
+
+    public function push($element): int
+    {
+        array_push($this->elements, $element);
+        return $this->size();
+    }
+
+    public function size(): int
+    {
+        return count($this->elements);
+    }
+
+    public function top()
+    {
+        return $this->elements[0];
+    }
+}
+
+function example_stack(): void
+{
+    /**
+     * @var Stack<int> $int_stack
+     */
+    $int_stack = new Stack();
+
+    $int_stack->push(4);
+    $int_stack->push(5);
+    $int_stack->push(7);
+
+    echo $int_stack->pop() . "\n"; // 7
+    echo $int_stack->size() . "\n"; // 2
+    echo $int_stack->top() . "\n"; // 4
+}
+
+example_stack();
+

contents/stacks_and_queues/stacks_and_queues.md

@@ -24,6 +24,8 @@ Here is a simple implementation of a stack:
 [import, lang:"cpp"](code/cpp/stack.cpp)
 {% sample lang="rust" %}
 [import, lang:"rust"](code/rust/Stack.rs)
+{% sample lang="php" %}
+[import, lang:"php"](code/php/stack.php)
 {% endmethod %}
 
 Here is a simple implementation of a queue:
@@ -36,6 +38,8 @@ Here is a simple implementation of a queue:
 [import, lang:"cpp"](code/cpp/queue.cpp)
 {% sample lang="rust" %}
 [import, lang:"rust" ](code/rust/Queue.rs)
+{% sample lang="php" %}
+[import, lang:"php"](code/php/queue.php)
 {% endmethod %}