Implement Stack and Queue in PHP

contents/stacks_and_queues/code/php/queue.php

@@ -0,0 +1,65 @@
+<?php
+/**
+ * The SplQueue class provides the main functionalities of a queue.
+ * It is integrated into the PHP SPL library which is usable in any PHP application.
+ *
+ * Note: top() reads from end of the doubly linked list
+ *       and will not return the first element. Use bottom() for that.
+ *
+ * @see https://www.php.net/manual/en/class.splqueue.php
+ */
+$queue = new SplQueue();
+
+$queue->enqueue(4);
+$queue->enqueue(5);
+$queue->enqueue(9);
+
+echo $queue->dequeue(), PHP_EOL; // 4 - First in first out
+echo $queue->count(), PHP_EOL;   // 2 - Elements in the queue
+echo $queue->top(), PHP_EOL;     // 9 - End of the doubly linked list
+echo $queue->bottom(), PHP_EOL;  // 5 - Begin of the doubly linked list
+
+// Implementation of own Queue
+
+interface QueueInterface
+{
+    public function enqueue($value);
+    public function dequeue();
+    public function front();
+    public function count();
+}
+
+class Queue implements QueueInterface
+{
+    private $queue = [];
+
+    public function enqueue($value)
+    {
+        $this->queue[] = $value;
+    }
+
+    public function dequeue()
+    {
+        return array_shift($this->queue);
+    }
+
+    public function front()
+    {
+        return reset($this->queue);
+    }
+
+    public function count()
+    {
+        return count($this->queue);
+    }
+}
+
+$queue = new Queue();
+
+$queue->enqueue(4);
+$queue->enqueue(5);
+$queue->enqueue(9);
+
+echo $queue->dequeue(), PHP_EOL; // 4 - First in first out
+echo $queue->count(), PHP_EOL;   // 2 - Elements in the queue
+echo $queue->front(), PHP_EOL;   // 5 - Begin of the array

contents/stacks_and_queues/code/php/stack.php

@@ -0,0 +1,69 @@
+<?php
+/**
+ * The SplStack class provides the main functionalities of a stack.
+ * It is integrated into the PHP SPL library which is usable in any PHP application.
+ *
+ * @see https://www.php.net/manual/en/class.splstack.php
+ */
+$stack = new SplStack();
+
+$stack->push(4);
+$stack->push(5);
+$stack->push(9);
+
+echo $stack->pop(), PHP_EOL;    // 9 - Last in first out
+echo $stack->count(), PHP_EOL;  // 2 - Elements in the stack
+echo $stack->top(), PHP_EOL;    // 5 - End of the doubly linked list
+echo $stack->bottom(), PHP_EOL; // 4 - Begin of the doubly linked list
+
+// Implementation of own Stack
+
+interface StackInterface
+{
+    public function push($value);
+    public function pop();
+    public function top();
+    public function bottom();
+    public function count();
+}
+
+class Stack implements StackInterface
+{
+    private $stack = [];
+
+    public function push($value)
+    {
+        $this->stack[] = $value;
+    }
+
+    public function pop()
+    {
+        return array_pop($this->stack);
+    }
+
+    public function top()
+    {
+        return end($this->stack);
+    }
+
+    public function bottom()
+    {
+        return reset($this->stack);
+    }
+
+    public function count()
+    {
+        return count($this->stack);
+    }
+}
+
+$stack = new Stack();
+
+$stack->push(4);
+$stack->push(5);
+$stack->push(9);
+
+echo $stack->pop(), PHP_EOL;    // 9 - Last in first out
+echo $stack->count(), PHP_EOL;  // 2 - Elements in the stack
+echo $stack->top(), PHP_EOL;    // 5 - End of the array
+echo $stack->bottom(), PHP_EOL; // 4 - Begin of the array

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 %}