mysql - PHP MySQLi doesn't execute INSERT query

I had a false redirect. But the system won't
let me delete the question
I have a website with a register
page. In the backend is a SQL database, but while UPDATE and SELECT work, INSERT
doesn't. IT also doesn't give me any errors.

The
code which makes the INSERT statement looks as
follows:

$username =
            "peter";
$pwhash = password_hash($password,
            PASSWORD_DEFAULT);

$role = "publisher";
$locked =
            "false";

//Prepare SQL Query
$sql = "insert into
            user(username, password, role, locked)";
$sql .= " VALUES (?, ?, ?,
            ?);";

//Reuire SQL Connection
require
            "db_inc.php";

//Prepare stmt
$stmt = mysqli_prepare($con,
            $sql);

//Bind Parameters
mysqli_stmt_bind_param($stmt,
            'ssss', 
 $username,
 $pwhash,
 $role,

            $locked);

//Execute
            SQL
mysqli_stmt_execute($stmt);


mysqli_close($con);

The
SQL database looks like this:
rel="nofollow noreferrer">

What am I doing wrong?
The $con connection is correct, as it workes on the SELECT and UPDATE
querys.