mysql_query() expects parameter 1 to be string, resource given
<?php

$password=(!isset($_POST['password']));
$username=(!isset($_POST['username']));

    $username = mysql_real_escape_string($username);
    $password = mysql_real_escape_string($password);

$query = mysql_query ("SELECT * FROM tb_funcionario WHERE username='$username' and password='$password'");

   $result = mysql_query($query);

   var_dump($result);

   $num_rows = $result->$num_rows;

    if ($num_rows)
    {
        echo "username already exist";
    }
    else
    {
     $query = "INSERT INTO tb_funcionario (nome_funcionario, username, password) VALUES (
    '$_POST[nome_funcionario]',
    '$_POST[username]',
    '$_POST[password]'
    )";;

       $result = mysql_query($query) or die (mysql_error());

    }


        mysql_query($query);
        mysql_close($bd_con);
?>

$query = mysql_query ("SELECT * FROM tb_funcionario WHERE username='$username' and password='$password'");

$result = mysql_query($query);

$query = mysql_query ("SELECT * FROM tb_funcionario WHERE
    username='$username' and password='$password'");

$result = mysql_query($query);

$query = "SELECT * FROM tb_funcionario WHERE
    username='$username' and password='$password'";

$result = mysql_query($query);

$query = mysql_query ("SELECT * FROM tb_funcionario WHERE username='$username' and password='$password'");
$result = mysql_query($query);

$query = "SELECT * FROM tb_funcionario WHERE username='$username' and password='$password'";
$result = mysql_query($query);

$query = mysql_query ("SELECT * FROM tb_funcionario WHERE username='$username' and password='$password'");
$result = mysql_query($query);

$query = "SELECT * FROM tb_funcionario WHERE username='$username' and password='$password'");
$result = mysql_query($query);

$query = mysql_query ("SELECT * FROM tb_funcionario WHERE username='$username' and    password='$password'");

$result = mysql_query($query);

$sql = "SELECT * FROM tb_funcionario WHERE username='$username' and password='$password'";

$result = mysql_query($sql);

$result = mysql_query( "SELECT * FROM tb_funcionario WHERE username='$username' and password='$password'"; );