Tidak bisa login dari login page php

Mohon bimbingannya, apakah ada yang salah dari script php saya ?

sehingga tidak bisa login di menu login page php.

selalu muncul user dan password salah terus. padahal di phpmyadmin sudah ada databasenya dengan login admin admin

terlampir script nya :

<?php

        include('admin/lib/dbcon.php');

dbcon();

session_start();

$username = $_POST['username'];

$password = $_POST['password'];

/*................................................ admin .....................................................*/

$query = "SELECT * FROM admin WHERE username='$username' AND password='$password'";

$result = mysqli_query($query)or die(mysqli_error());

$row = mysqli_fetch_array($result);

$num_row = mysqli_num_rows($result);

/*...................................................Technical Staff ..............................................*/

$query_client = mysqli_query("SELECT * FROM client WHERE username='$username' AND password='$password'")or die(mysqli_error());

$num_row_client = mysqli_num_rows($query_client);

$row_client = mysqli_fetch_array($query_client);

if( $num_row > 0 ) {

$_SESSION['id']=$row['admin_id'];

echo 'true_admin';

mysqli_query("insert into user_log (username,login_date,admin_id)values('$username',NOW(),".$row['admin_id'].")")or die(mysqli_error());

}else if ($num_row_client > 0){

$_SESSION['client']=$row_client['client_id'];

echo 'true';

mysqli_query("insert into user_log (username,login_date,client_id)values('$username',NOW(),".$row_client['client_id'].")")or die(mysqli_error());

}else{

echo 'false';

}

?>