diff --git a/includes/functions.php b/includes/functions.php
new file mode 100644
index 0000000..2833564
--- /dev/null
+++ b/includes/functions.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+function sanitize(string $value): string
+{
+    return htmlspecialchars(
+        trim($value),
+        ENT_QUOTES,
+        'UTF-8'
+    );
+}
+
+function usernameToFolder(
+    string $username
+): string {
+
+    return preg_replace(
+        '/[^a-zA-Z0-9_-]/',
+        '',
+        strtolower($username)
+    );
+}
+
+function userPath(
+    string $username
+): string {
+
+    return USERS_PATH .
+        '/' .
+        usernameToFolder($username);
+}
\ No newline at end of file