php向数据库插入数据

<?php
header("Content-type: text/html;charset=utf-8");
$con = mysql_connect("localhost","root","root");//连接数据库
if (!$con){
  die('Could not connect: ' . mysql_error());
}
mysql_select_db("web", $con);//打开数据库
mysql_query("set names utf8");
$sql="INSERT INTO users (username, password)
VALUES
('$_POST[username]','$_POST[password]')";//插入数据
if (!mysql_query($sql,$con)){
  die('Error: ' . mysql_error());
  echo "0";
}
echo "1";
mysql_close($con);
?>