<?php
ob_start();
$host="localhost"; // Host name
$username="kirby"; // Mysql username
$password="*****"; // Mysql password
$db_name="honpou"; // Database name
$tbl_name="usuarios"; // Table name

// Connect to server and select databse.
$dbc = @mysqli_connect("$host", "$username", "$password", "$db_name")or die("cannot connect");

// Define $myusername and $mypassword
$myusername=$_POST['username'];
$mypassword=$_POST['password'];

$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysqli_real_escape_string($dbc, $myusername);
$mypassword = mysqli_real_escape_string($dbc, $mypassword);

$sql="SELECT * FROM $tbl_name WHERE nickname='$myusername' and password='$mypassword'";
$result=mysqli_query($dbc, $sql);

/*******************************
Esta es la primary key de usuario, quiero obtenerla para después usarla en otros .php:
$query="SELECT id FROM $tbl_name WHERE nickname='$myusername' and password='$mypassword'";
$userid = mysqli_query($dbc, $query);
Supongo que con esto lo obtendría y se guardaría en $userid, pero... ya la puedo llamar desde otra página para hacer otro query?
*******************************/

// Mysql_num_row is counting table row
$count=mysqli_num_rows($result);
// If result matched $myusername and $mypassword, table row must be 1 row

if($count==1){
// Register $myusername, $mypassword and redirect to file "login_success.php"
session_start();
$_SESSION['username'] = $username;
$_SESSION['password'] = $password;
header("location:profile.php");
}
else {
echo "Wrong Username or Password";
}

ob_end_flush();
?>