Implement user authentication and registration; enhance error handling and database interaction in API

public/test.php

@@ -1,7 +1,14 @@
 <?php
 
-foreach($_SERVER as $key => $value) {
+/*foreach($_SERVER as $key => $value) {
     echo $key . " === " . $value . "<br>";
-}
+}*/
 
-//echo $_SERVER["HTTP_X_API_KEY"];
+//echo $_SERVER["HTTP_X_API_KEY"];
+
+$string = '{"user":"marc", "auth":true}';
+$secret = "281361f952279bd9530734c67ed04aed2756f0fe00cb998cd6c28324f491484c";
+
+echo "Hash: " . hash_hmac("sha256", $string, $secret);
+
+echo "Decode: " . hash_equals($string, $secret);