Singleton added

src/Pattern/Creational/Singleton.php

@@ -0,0 +1,105 @@
+<?php
+
+/**
+ * @package: patterns
+ * @author: Yevhen Odynets
+ * @date: 2025-07-03
+ * @time: 07:00
+ */
+
+declare(strict_types = 1);
+
+namespace Pattern\Creational;
+
+use RuntimeException;
+
+/**
+ * The Singleton class defines the `GetInstance` method that serves as an
+ * alternative to constructor and lets clients access the same instance of this
+ * class over and over.
+ */
+class Singleton
+{
+    /**
+     * The Singleton's instance is stored in a static field. This field is an
+     * array, because we'll allow our Singleton to have subclasses. Each item in
+     * this array will be an instance of a specific Singleton's subclass. You'll
+     * see how this works in a moment.
+     */
+    private static array $instances = [];
+
+    public ?string $value = null;
+
+    /**
+     * The Singleton's constructor should always be private to prevent direct
+     * construction calls with the `new` operator.
+     */
+    protected function __construct() {}
+
+    /**
+     * This is the static method that controls the access to the singleton
+     * instance. On the first run, it creates a singleton object and places it
+     * into the static field. On subsequent runs, it returns the client existing
+     * object stored in the static field.
+     *
+     * This implementation lets you subclass the Singleton class while keeping
+     * just one instance of each subclass around.
+     */
+    public static function getInstance(?string $message = null): Singleton
+    {
+        $cls = static::class;
+
+        /** @noinspection ForgottenDebugOutputInspection */
+        dump(trim($message . ': ' . $cls, ' :'));
+
+        if (!isset(self::$instances[$cls])) {
+            self::$instances[$cls] = new static();
+        }
+
+        return self::$instances[$cls];
+    }
+
+    /**
+     * Singletons should not be restorable from strings.
+     */
+    public function __wakeup()
+    {
+        throw new RuntimeException("Cannot unserialize a singleton.");
+    }
+
+    /**
+     * Finally, any singleton should define some business logic, which can be
+     * executed on its instance.
+     */
+    public function someBusinessLogic(): void
+    {
+        echo 'I AM SINGLETON: ' . date('H:i:s') . '<br>';
+    }
+
+    /**
+     * Singletons should not be cloneable.
+     */
+    protected function __clone() {}
+
+    /**
+     * @return string|null
+     */
+    public function getValue(): ?string
+    {
+        return $this->value;
+    }
+
+    /**
+     * @param  string|null  $value
+     *
+     * @return $this
+     */
+    public function setValue(?string $value): static
+    {
+        $this->value = $value;
+
+        return $this;
+    }
+}
+
+

src/Pattern/Creational/Sub/Single.php

@@ -0,0 +1,24 @@
+<?php
+
+/**
+ * @package: patterns
+ * @author: Yevhen Odynets
+ * @date: 2025-07-03
+ * @time: 10:22
+ */
+
+//phpcs:ignore
+declare(strict_types = 1);
+namespace Pattern\Creational\Sub;
+
+use Contracts\SingleInterface;
+use Pattern\Creational\Singleton;
+
+class Single extends Singleton implements SingleInterface
+{
+    public function childish(): void
+    {
+        /** @noinspection ForgottenDebugOutputInspection */
+        dump(__METHOD__);
+    }
+}