Passing JSON object built from SQL from PHP to JavaScript

I am trying to pass a JSON object from PHP to Javascript. the object is being filled from an SQL Database here is the PHP code I am using.

<?php
    $conn = mysql_connect("localhost","root","");
    if(! $conn )
    {
         die('Could not connect: ' . mysql_error());
    }
    mysql_select_db('db') or die( 'Error'. mysql_error() );
    $query = "SELECT * FROM products;";
    $results = mysql_query($query, $conn);
    $return = array();

    while($result = mysql_fetch_assoc($results))
    {
        $mount = array('product_code' => $results['product_code'], 'colour'  =>    $results['colour'], 'price' => $results['price']);
        array_push($return, $mount);
    }

    return json_encode($return);
?>

I have changed a few of the variable names but the same functionality is there.

now when I try to do an AJAX Get to this .php file it crashes at the JSON.Parse part code shown below:

$.get("JSON.php", function(data) {
    var JSONdata = JSON.parse(data);
    alert(JSONdata[0].colour);
});

My alert is there just for testing. I Understand the problem may lie in my building of the $return array. Rather new to JSON, any help would be greatly appreciated.

EDIT: taking all the information from below I have corrected my PHP code to look as such.

<?php
    $conn = mysql_connect("localhost","root","");
    $error = array("result" => false, "error" => mysql_error());

    if(! $conn )
    {
        die(json_encode($error));
    }
    mysql_select_db('db') or die(json_encode($error));
    $query = "SELECT * FROM products;";
    $results = mysql_query($query, $conn);
    $return = array();

    while($result = mysql_fetch_assoc($results))
    {
        $mount = array('product_code' => $result['product_code'], 'colour'  => $result['colour'], 'price' => $result['price']);
        array_push($return, $mount);
    }

    echo json_encode($return);
?>

I'm Looking into changing the mysql_* functions to new more compatible versions