Error trying to create login system
<p>I've been trying to create a login system in PHP.
I've managed to successfully to connect the database but I'm got a problem saying</p>

<blockquote>
  <p>Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\xampp1\htdocs\login\check.php on line 23<br>
  Wrong username or password are wrong
  Notice: Undefined property: mysqli::$close in C:\xampp1\htdocs\login\check.php on line 36</p>
</blockquote>

<p>My code is:</p>

<pre><code>&lt;html&gt;
&lt;head&gt;
  &lt;title&gt;Login Page&lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
  &lt;form method="post" action="check.php" &gt;
    &lt;table&gt;
      &lt;tr&gt;
        &lt;td&gt;&lt;label&gt;Username&lt;/label&gt;&lt;/td&gt;
        &lt;td&gt;&lt;input type="text" name="username"&gt;&lt;/td&gt;
      &lt;/tr&gt;
      &lt;tr&gt;
        &lt;td&gt;&lt;label&gt;password&lt;/label&gt;&lt;/td&gt;
        &lt;td&gt;&lt;input type="text" name="password"&gt;&lt;/td&gt;
      &lt;/tr&gt;
      &lt;tr&gt;
        &lt;td&gt;&lt;input type="submit" value="submit"&gt;&lt;/td&gt;
      &lt;/tr&gt;
    &lt;/table&gt;
  &lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;

&lt;?php
ob_start();
$username= $_POST['username'];
$password= $_POST['password'];

$servername= "localhost";
$username= "root";
$password = "";
$dbname="login";

$conn= mysqli_connect($servername,$username,$password,$dbname);

if (!$conn){
    die("Not connected". mysqli_connect_error);
}else{
    echo "connection sucessful";

}

$sql= "select * from details where $username=username and $password=password";

$result=mysql_query($sql);
$count=mysql_num_rows($result);



if ($count == 1){
    header("location:sucess.php");
}else{
    echo "Wrong username or password are wrong";


}
$conn-&gt;close;
ob_end_flush();
</code></pre>