I'm not able to start session_start () in php and I really can't understand the reason, I've tried a few things people suggested on forums, but the session_start() still does not work
index file where are not retrieving variables $ _SESSION:
<?php
session_start();
?>
<!DOCTYPE html>
<html>
<head>
    <title>Pagina1</title>
    <link rel="stylesheet" href="css/style.css"/>
</head>
<body>
    <article id="newPrincipal">
        <h1>Usuário id:<?php echo $_SESSION['userId']; ?></h1> 
    </article>
    <h1>Result:<?php echo "Usuário id:".$_SESSION['userId']; ?></h1>
</body>
</html>
<?php
echo '<pre>';
print_r($_SESSION['userId']);
echo '</pre>';login file:
<?php
if(isset($_POST['login-submit'])){
    require 'dbh.inc.php';
   $users = $_POST['nome'];
    $mailuid = $_POST['mailuid'];
    $password = $_POST['pwd'];
    $token;
    if(empty($mailuid) || empty($password)){
        header("Location: ../header.php=emptyfields");
        exit();
    }
    else{
        $sql = "SELECT * FROM users WHERE Usuarios=? AND email=?";
        $stmt = mysqli_stmt_init($conn);
        if(!mysqli_stmt_prepare($stmt, $sql)){
            header("Location: ../index.php?error=sqlerror");
            exit();
        }
        else{
            mysqli_stmt_bind_param($stmt, "ss", $mailuid, $users);
            mysqli_stmt_execute($stmt);
            $result = mysqli_stmt_get_result($stmt);
            if($row = mysqli_fetch_assoc($result)){
                $pwdCheck = password_verify($password, $row['pwdUsers']);
                if($pwdCheck == false){
                    header("Location: ../header.php?error=wrongpwd");
                    exit();
                }
                else if($pwdCheck == true){
                    session_start();
                    $_SESSION['userId'] = $row['idUsers'];
                    $_SESSION['userId2'] = $row['uidUsers'];
                    $_SESSION['email'] = $row['emailUsers'];
                    header("Location: ../index.php?login=".$_SESSION['userId']);
                }
                else{
                    header("Location: ../login.php?error=wrongpwd");
                    exit();
                }
            }
        }
    }
}
else{
    header("Location: ../index.php");
}I'm using an external server not the Xampp / Wamp, I do not know if this would imply anything ...
I tried every ways to retrieve some information using $ _SESSION in the index file, but I could not.
 
     
    