Initial habit tracker project

app/helpers.php

@@ -0,0 +1,82 @@
+<?php
+
+function config(string $key, $default = null)
+{
+    static $config = null;
+
+    if ($config === null) {
+        $config = require __DIR__ . '/../config/config.php';
+    }
+
+    $parts = explode('.', $key);
+    $value = $config;
+
+    foreach ($parts as $part) {
+        if (!is_array($value) || !array_key_exists($part, $value)) {
+            return $default;
+        }
+        $value = $value[$part];
+    }
+
+    return $value;
+}
+
+function e(?string $value): string
+{
+    return htmlspecialchars($value ?? '', ENT_QUOTES, 'UTF-8');
+}
+
+function redirect(string $route): never
+{
+    header('Location: index.php?route=' . urlencode($route));
+    exit;
+}
+
+function current_user_id(): ?int
+{
+    return $_SESSION['user_id'] ?? null;
+}
+
+function require_login(): void
+{
+    if (!current_user_id()) {
+        redirect('login');
+    }
+}
+
+function flash(string $key, ?string $message = null): ?string
+{
+    if ($message !== null) {
+        $_SESSION['flash'][$key] = $message;
+        return null;
+    }
+
+    $value = $_SESSION['flash'][$key] ?? null;
+    unset($_SESSION['flash'][$key]);
+    return $value;
+}
+
+function csrf_token(): string
+{
+    if (empty($_SESSION['csrf_token'])) {
+        $_SESSION['csrf_token'] = bin2hex(random_bytes(32));
+    }
+
+    return $_SESSION['csrf_token'];
+}
+
+function csrf_field(): string
+{
+    return '<input type="hidden" name="csrf_token" value="' . e(csrf_token()) . '">';
+}
+
+function verify_csrf_token(): void
+{
+    $token = $_POST['csrf_token'] ?? '';
+
+    if (!is_string($token) || !hash_equals($_SESSION['csrf_token'] ?? '', $token)) {
+        http_response_code(419);
+        echo 'Sicherheitspruefung fehlgeschlagen. Bitte lade die Seite neu.';
+        exit;
+    }
+}