php - Users in my social network can't register and login -

i made simple social network system, register , login function, whem user register , try login, give message:

fatal error: call member function rowcount() on non-object in home/login.php on line 7

i'm using pdo connection.

there problem in login.php code?:

<?php include('dbcon.php'); $username = $_post['username']; $password = $_post['password'];  $query = $conn->query("select * database username = '$username' , password = '$password'"); $count = $query->rowcount(); $row = $query->fetch(); if ($count > 0){ session_start(); $_session['id'] = $row['member_id'];  header('location:home.php');  }else{  header('location:index.php');  } ?> 

i assuming using pdo, , rowcount method not exist, on other hand there rowcount method. remember these case-sensitive.

<?php include('dbcon.php'); $username = $_post['username']; $password = $_post['password'];  $stm = $conn->prepare("select * database username = ? , password = ?"); $stm->execute(array($username, $password)); $count = $stm->rowcount(); $row = $stm->fetch(pdo::fetch_assoc); if ($count > 0) {     session_start();     $_session['id'] = $row['member_id'];     header('location:home.php');  } else {     header('location:index.php');  } ?> 

this should trick.
pdostatement::rowcount

i edited query, uses prepared statement placeholders, protect sql injection.