问绑定的PHP select语句

EN

$email = $_POST['email'];
$password = $_POST['password']; 
$selectStatement = "SELECT id FROM users WHERE email = ? ";
$stmts = mysqli_prepare($dbc, $selectStatement);
mysqli_stmt_bind_param($stmts,'s', $email);
mysqli_stmt_execute($stmts);
$count = mysqli_stmt_num_rows($stmts);

if (!$stmts){
    die('mysqli error: '.mysqli_error($dbc));
}
while($row = mysqli_stmt_fetch($stmts)){
    if($row != null){   
        echo('User already registered!');
    }
    }else{  
        $insertQuery = "INSERT INTO users(email, password) VALUES(?, ?)";
        $stmtI = mysqli_prepare($dbc, $insertQuery); 
        mysqli_stmt_bind_param($stmtI, "ss", $email, $password);
        mysqli_stmt_execute($stmtI);
        echo('Registration completed!');
}
}
mysqli_stmt_close($stmts);  
mysqli_stmt_close($stmtI);
mysqli_close($dbc);