<?php
$link = mysqli_connect('localhost', 'root', 'root');
mysqli_select_db($link, 'code');
$table = addslashes($_GET['table']);
$sql = "UPDATE `{$table}`
SET `username`='admin'
WHERE id=1";
if(!mysqli_query($link, $sql)) {
echo(mysqli_error($link));
}
mysqli_close($link);