Как отправить переменую?

<?php
require 'rb.php';
$connect = mysqli_connect("127.0.0.1", "root", "", "title");
echo "новое название";
 
?>
<form action="" method="POST" ><input type="text" name="title"><hr><button type="submit"  name="do_signup">изменить</button></form>
<?php 
$test=$_POST;
$t = $test['title'];
if (isset($test['do_signup']) ) {
mysqli_query($connect, "INSERT INTO `title` (`id`, `title`) VALUES (NULL, $t");
 
}
 ?>

<?php
require 'rb.php';
$connect = mysqli_connect("127.0.0.1", "root", "", "title");
echo "новое название";
 
?>
<form action="" method="POST" ><input type="text" name="title"><hr><button type="submit"  name="do_signup">изменить</button></form>
<?php 
if (isset($_POST['title']) ) {
    $title = $_POST['title'];
    $stmt = mysqli_prepare($connect, 'INSERT INTO `title` (`title`) VALUES (?)';
    mysqli_stmt_bind_param($stmt, 's', $title);
    mysqli_stmt_execute($stmt);
}