<form action="sample.php" method="POST">
<input name="sample" type="text">
<input name="submit" type="submit" value="Submit">
</form>

<?php

if (isset($_POST['submit'])) {

    $mysqli = new mysqli('localhost', 'user', 'password', 'mysampledb');

    /* check connection */
    if (mysqli_connect_errno()) {
        printf("Connect failed: %s
", mysqli_connect_error());
        exit();
    }

    $stmt = $mysqli->prepare("INSERT INTO SampleTable VALUES (?)");
    $stmt->bind_param('s', $sample);   // bind $sample to the parameter

    $sample = isset($_POST['sample'])
              ? $_POST['sample']
              : '';

    /* execute prepared statement */
    $stmt->execute();

    printf("%d Row inserted.
", $stmt->affected_rows);

    /* close statement and connection */
    $stmt->close();

    /* close connection */
    $mysqli->close();
}

?>