<?php
# DB

$host = 'localhost';
$user = 'root';
$pass = '';
$dbname = 'sql';

# Conexion

$db = mysql_connect($host, $user, $pass);
mysql_select_db($dbname,$db);

$sql = "SELECT * FROM users WHERE id=".$_GET['id'];
$query = @mysql_query($sql);
if(@mysql_num_rows($query)==0)
{
   echo "No hay columnas<br>";
}

$fetch=@mysql_fetch_row($query);
echo "ID: ".$fetch[0]."<br>";
echo "Username: ".$fetch[1]."<br>";

?>