Added signup form and revamped phonebook.

vendor/vlucas/phpdotenv/src/Repository/Adapter/WriterInterface.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Dotenv\Repository\Adapter;
+
+interface WriterInterface
+{
+    /**
+     * Write to an environment variable, if possible.
+     *
+     * @param non-empty-string $name
+     * @param string           $value
+     *
+     * @return bool
+     */
+    public function write(string $name, string $value);
+
+    /**
+     * Delete an environment variable, if possible.
+     *
+     * @param non-empty-string $name
+     *
+     * @return bool
+     */
+    public function delete(string $name);
+}