Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\register.php on line 22

[phpperson]

The code you are about to see is for a register page and i keep getting this error Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\register.php on line 22 could someone HELP!!!!!!!!: <?php

 

require 'datebase.inc.php';

require'thecore.inc.php';

 

if(!loggedin()) {

 

 if(isset($_POST['username'])&&isset($_POST['surname'])&&isset($_POST['password'])&&isset($_POST['password_again'])) {

$Username = $_POST['username'];

$Surname = $_POST['surname'];

$Password = $_POST['password'];

$password_again = $_POST['password_again'];

if (!empty($Username)&&!empty($Surname)&&!empty($Password)&&!empty($password_again)){

if ($Password!==$password_again) {

echo 'Password does not match';

}else{

 

$query = "SELECT `username` FROM `user` WHERE `username` = '$Username'";

$query_run = mysql_query($query);

 

 

if(mysql_num_rows($query_run)==1) {

echo 'The username'.$Username.'already exists.'; 

}else{

echo 'OK';

}

}

}else{

echo 'Fill in the fields';

}

 

 }

 }

 

?>

<form action="register.php" method="POST">

<input  type="text" name="username" placeholder="Username..." value="<?php echo $Username;?>">

<input   type="text" name="surname" placeholder=" Surname... "  value="<?php echo $Surname;?>"><br><br>

<input   type="password" name="password" placeholder=" Password..."><br><br>

<input  type="password" name="password_again" placeholder=" Password again..."><br><br>

<input type="submit" Value="Register">

</form> 

[jcbones]

Your query is failing, and returning a boolean false, not a resource.  Check mysql_error() for the failure, then change everything to mysqli or PDO

[phpperson]

Your query is failing, and returning a boolean false, not a resource.  Check mysql_error() for the failure, then change everything to mysqli or PDO

I fixed