migrazione PHP 5 -> 7 - autorizzazione fallita

[nicemotion]

Ho migrato l'intero gestionale (+200 files) da PHP 5.5 a 7.4 e funziona tutto tranne questo file di autorizzazione che girava sotto la versione precedente ma non sotto la 7 e non riesco a trovare la funzione incompatibile (php non me lo segnala)

Lo posto commentato :

ini_set('display_errors', '1');
ini_set('display_startup_errors', '1');
error_reporting(E_ALL);

ini_set('session.gc_maxlifetime', '6000');
if (!isset($_SESSION)) {
  session_start();
}
$MM_authorizedUsers = "";
$MM_donotCheckaccess = "true";

// *** Restrict Access To Page: Grant or deny access to this page
function isAuthorized($strUsers, $strGroups, $UserName, $UserGroup) {
  // For security, start by assuming the visitor is NOT authorized.
  $isValid = False;

  // When a visitor has logged into this site, the Session variable MM_Username set equal to their username.
  // Therefore, we know that a user is NOT logged in if that Session variable is blank.
  if (!empty($UserName)) {
    // Besides being logged in, you may restrict access to only certain users based on an ID established when they login.
    // Parse the strings into arrays.
   
    $arrUsers = Explode(",", $strUsers);
    $arrGroups = Explode(",", $strGroups);
  if (in_array($UserName, $arrUsers)) {
      $isValid = true;
    }

    // Or, you may restrict access to only certain users based on their username.
    if (in_array($UserGroup, $arrGroups)) {
      $isValid = true;
    }
    if (($strUsers == "") && true) {
      $isValid = true;
    }
  }
  return $isValid;
}

$MM_restrictGoTo = "loginSorry.php";
if (!((isset($_SESSION['MM_Username'])) && (isAuthorized("",$MM_authorizedUsers, $_SESSION['MM_Username'], $_SESSION['MM_UserGroup'])))) {  
  $MM_qsChar = "?";
  $MM_referrer = $_SERVER['PHP_SELF'];
  if (strpos($MM_restrictGoTo, "?")) $MM_qsChar = "&";
  if (isset($QUERY_STRING) && strlen($QUERY_STRING) > 0)
  $MM_referrer .= "?" . $QUERY_STRING;
  $MM_restrictGoTo = $MM_restrictGoTo. $MM_qsChar . "accesscheck=" . urlencode($MM_referrer);
  header("Location: ". $MM_restrictGoTo);
  exit;
}

if($_SESSION['MM_UserGroup'] < 4)
{header("Location: Pub_loginSorry.php");
}
/* echo "--------------------------------------------------------- gc_maxlifetime -> ".ini_get('session.gc_maxlifetime');*/ 

Questa la pagina di accesso:

if (!isset($_SESSION)) {
  session_start();
}

$loginFormAction = $_SERVER['PHP_SELF'];
if (isset($_GET['accesscheck'])) {
  $_SESSION['PrevUrl'] = $_GET['accesscheck'];
}

if (isset($_POST['username'])) {
  $loginUsername=mysqli_real_escape_string($tao_conn, $_POST['username']);
  $password=mysqli_real_escape_string(sha1($tao_conn, $_POST['password']));
  $MM_fldUserAuthorization = "AuthLev";
  $MM_redirectLoginSuccess = "index.php";
  $MM_redirectLoginFailed = "loginSorry.php";
  $MM_redirecttoReferrer = false;
  mysqli_select_db($tao_conn, $database_tao_conn);$LoginRS__query=sprintf("SELECT username, password, AuthLev FROM adminauth WHERE username=%s AND password=%s",
  GetSQLValueString($tao_conn,$loginUsername, "text"), GetSQLValueString($tao_conn,$password, "text")); 
   
  $LoginRS = mysqli_query($tao_conn,$LoginRS__query) or die(mysqli_error($tao_conn));
  $loginFoundUser = mysqli_num_rows($LoginRS);
  if ($loginFoundUser) {
    
    $loginStrGroup  = mysqli_result($LoginRS,0,'AuthLev');
    
    if (PHP_VERSION >= 5.1) {session_regenerate_id(true);} else {session_regenerate_id();}
    //declare two session variables and assign them
    $_SESSION['MM_Username'] = $loginUsername;
    $_SESSION['MM_UserGroup'] = $loginStrGroup;          

    if (isset($_SESSION['PrevUrl']) && false) {
      $MM_redirectLoginSuccess = $_SESSION['PrevUrl'];    
    }
    header("Location: " . $MM_redirectLoginSuccess );
  }
  else {
    header("Location: ". $MM_redirectLoginFailed );
  }