如何将字符串添加到MYSQL数据库,并使用php删除其中的字符串的最后一个字符？

$string = "Hello, world!";
$last_char = substr($string, -1);
$new_string = $last_char . $string;

// 插入新字符串到MySQL数据库
$conn = mysqli_connect("localhost", "username", "password", "database_name");
$sql = "INSERT INTO table_name (column_name) VALUES ('" . $new_string . "')";
if (mysqli_query($conn, $sql)) {
    echo "字符串已成功添加到数据库";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

mysqli_close($conn);