violates dependency inversion

Basic/Solid/MySQLConnection.php

@@ -0,0 +1,7 @@
+<?php
+
+class MySQLConnection {
+  public function connect() {
+    return 'Database connection';
+  }
+}

Basic/Solid/PasswordRemider.php

@@ -0,0 +1,9 @@
+<?php
+
+class PasswordRemider { // high-level module
+  private $dbConnection;
+
+  public function __construct(MySQLConnection $dbConnection) { // low-level module (1. violates denpend on abstraction, not on concretions, 2. violates the open-closed principle when database changes)
+    $this->dbConnection = $dbConnection;
+  }
+}

Basic/Solid/doc.md

@@ -14,4 +14,6 @@ This means that every subclass or derived class should be substitutable for thei
 
 # Interface Segregation Principle
 A client should never be forced to implement an interface that it doesn’t use, or clients shouldn’t be forced to depend on methods they do not use.
+# Dependency Inversion Principle
+Entities must depend on abstractions, not on concretions. It states that the high-level module must not depend on the low-level module, but they should depend on abstractions.