Use PHP constructor property promotion

Author: petk

_posts/06-02-01-Basic-Concept.md

@@ -29,18 +29,16 @@ class MysqlAdapter {}
 {% endhighlight %}
 
 This code can be refactored to use Dependency Injection and therefore loosen the dependency.
+Here, we inject the dependency in a constructor and use the [constructor property promotion][php-constructor-promotion] so it is available as a property across the class:
 
 {% highlight php %}
 <?php
 namespace Database;
 
 class Database
 {
-    protected $adapter;
-
-    public function __construct(MySqlAdapter $adapter)
+    public function __construct(protected MySqlAdapter $adapter)
     {
-        $this->adapter = $adapter;
     }
 }
 
@@ -50,3 +48,5 @@ class MysqlAdapter {}
 Now we are giving the `Database` class its dependency rather than creating it itself. We could even create a method
 that would accept an argument of the dependency and set it that way, or if the `$adapter` property was `public` we
 could set it directly.
+
+[php-constructor-promotion]: https://www.php.net/manual/en/language.oop5.decon.php#language.oop5.decon.constructor.promotion

_posts/06-03-01-Complex-Problem.md

@@ -82,11 +82,8 @@ namespace Database;
 
 class Database
 {
-    protected $adapter;
-
-    public function __construct(AdapterInterface $adapter)
+    public function __construct(protected AdapterInterface $adapter)
     {
-        $this->adapter = $adapter;
     }
 }
 

_posts/07-04-01-Interacting-via-Code.md

@@ -70,11 +70,8 @@ include 'views/foo-list.php';
 <?php
 class FooModel
 {
-    protected $db;
-
-    public function __construct(PDO $db)
+    public function __construct(protected PDO $db)
     {
-        $this->db = $db;
     }
 
     public function getAllFoos() {