env returns an environment variable

src/helpers.php

@@ -1,2 +1,8 @@
 <?php
 
+if (!function_exists('env')) {
+    function env(string $name): ?string
+    {
+        return $_ENV[$name];
+    }
+}

tests/EnvironmentTest.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Tests\Opdavies\PhpHelpers;
+
+use PHPUnit\Framework\TestCase;
+
+class EnvironmentTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        // Ensure that the enviornment variables are empty before each test.
+        $_ENV = [];
+    }
+
+    /** @test */
+    public function it_gets_an_environment_variable()
+    {
+        $_ENV['APP_ENV'] = 'prod';
+
+        $this->assertSame('prod', env('APP_ENV'));
+    }
+}