data transfer from php to javascript using json_encode

Question

I am building a Google maps page that uses lat long data coordinates to create a heat map to show the proliferation of foxes in an area.

As it currently stands, my app works fine when the lat long values are hard coded into my JavaScript function get_points on my index.php like this.

index.php (NB: This code works if tested but requires a google maps api key to load map and heatmap points)





 
   Heatmaps

The problem is, I don't want to hardcode the lat long coordinates in my get_points() function.

I am having bother serving these lat long points from my MySQL table to the said function using a php function I designed which uses json_encode.

I am getting errors mainly saying "not a valid MVC array". Yet strangely, I can print the array out.

My Table Schema

db table

My Custom PHP function

function get_coordinates() {
        $coordinates = array(); // initial decleration of memory 
        $latitudes = array(); // see above
        $longitudes = array(); // see above

        // Select all the rows in the location_values table
        $hotpointquery = query("SELECT `locationLatitude`, `locationLongitude` FROM `location_values` ");
        confirm($hotpointquery);

        while ($row = fetch_array($hotpointquery)) {
            $latitudes[] = $row['locationLatitude'];
            $longitudes[] = $row['locationLongitude'];

            // instantiate new map php array which is a COMBINATION of $latitudes and $longitudes and google map object. 
            $coordinates[] = 'new google.maps.LatLng(' . $row['locationLatitude'] .','. $row['locationLongitude'] .'),';  

            //convert the PHP array into JSON format, so it works with javascript
            $json_array = json_encode($coordinates);
        }

        //this block removes comma in very last lat lang element in our db
        $lastcount = count($coordinates)-1; // dorman : counts all lat lang in the databse n-1;
        $coordinates[$lastcount] = trim($coordinates[$lastcount], ",");  // for each pair, use trim function to remove the white space and comma in the last element of our lat lang at end of db

        // echo print_r($coordinates[$lastcount]); // this only prints out one set of lat langs
} // end of function/////////////

new_get_points()

function getPoints() {
  var array = 
}

miken32 · Accepted Answer

JSON is a data exchange format, not a programming language. When you include something like "new google.maps.LatLng..." in a string, that's all it is: a string. It doesn't mean anything – and even if it did, your PHP code isn't returning anything, and your JavaScript code isn't executing anything.

You are sort of on the right track though, so let's make some small changes.

In your PHP, you can do this:



Later in the page, within the

data transfer from php to javascript using json_encode

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