<?php
$offset = $argv[0];
session_start();
if(!empty($_POST['regusername']))
{
  $connect = mysqli_connect("", "", "", "");
$output = '';
$username = mysqli_real_escape_string($connect, $_POST['regusername']);
$email = mysqli_real_escape_string($connect, $_POST['regemail']);
$password = mysqli_real_escape_string($connect, $_POST['regpassword']);
$name = mysqli_real_escape_string($connect, $_POST['regname']);
$age = mysqli_real_escape_string($connect, $_POST['regage']);
$disease = mysqli_real_escape_string($connect, $_POST['regdis']);

$check = mysqli_query($connect, "SELECT * FROM users WHERE username = '$username' $offset");
$checkrows = mysqli_num_rows($check);

if($checkrows > 0)
{
  echo 'No';
}
else
{
  $query = "INSERT INTO users(username, password, email, name, age, disease) VALUES('$username', '$password', '$email', '$name', '$age', '$disease') $offset";
if(mysqli_query($connect, $query))
{
  echo 'Yes';
  $_SESSION['regusername'] = $_POST['regusername'];
 }
}
}
?>