PHP Query issue in setting values?

Quick question. I've got a SQL query which works with my database. However, I am to sure how to set parameters in my PHP file so that it works with my query?

Any Ideas? I'm having trouble with the Set parameters in terms of php and making my query work.

<?php

/*
 * Following code will list all the products
 */

// array for JSON response
$response = array();

// include db connect class
require_once __DIR__ . '/db_connect.php';

// connecting to db
$db = new DB_CONNECT();

set $orig_lat=51.42; 
set $orig_long=-0.550; 
set $bounding_distance=1;

// get all products from products table
$result = mysql_query(" SELECT * ,((ACOS(SIN($orig_lat * PI() / 180) * SIN(`latitude` * PI() /
180) + COS($orig_lat * PI() / 180) * COS(`latitude` * PI() / 180) *
COS(($orig_long - `longitude`) * PI() / 180)) * 180 / PI()) * 60 *
1.1515) AS `distance` FROM `Location` WHERE ( `latitude` BETWEEN
($orig_lat - $bounding_distance) AND ($orig_lat + $bounding_distance)
AND `longitude` BETWEEN ($orig_long - $bounding_distance) AND
($orig_long + $bounding_distance) ) ORDER BY `distance` ASC limit 1") or die(mysql_error()); 

// check for empty result
if (mysql_num_rows($result) > 0) {
    // looping through all results
    // products node
    $response["Location"] = array();

    while ($row = mysql_fetch_array($result)) {
        // temp user array
       $Location = array();
       $Location["id"] = $row["id"];
       $Location["latitude"] = $row["latitude"];
       $Location["longitude"] = $row["longitude"];



        // push single product into final response array
        array_push($response["Location"], $Location);
    }
    // success
    $response["success"] = 1;

    // echoing JSON response
    echo json_encode($response);
} else {
    // no products found
    $response["success"] = 0;
    $response["message"] = "No Profiles found";

    // echo no users JSON
    echo json_encode($response);
}
?>