Question

I’m trying to write a script in PHP that will accept a Bing maps quadkey and then return the zoom level, x-coordinate and y-coordinate so that I can use my own maps. I’ve based my code off the C# example code provided by Microsoft as such here:

public static void QuadKeyToTileXY(string quadKey, out int tileX, out int tileY, out int levelOfDetail)
{
    tileX = tileY = 0;
    levelOfDetail = quadKey.Length;
    for (int i = levelOfDetail; i > 0; i--)
    {
        int mask = 1 << (i - 1);
        switch (quadKey[levelOfDetail - i])
        {
            case '0':
                break;

            case '1':
                tileX |= mask;
                break;

            case '2':
                tileY |= mask;
                break;

            case '3':
                tileX |= mask;
                tileY |= mask;
                break;

            default:
                throw new ArgumentException("Invalid QuadKey digit sequence.");
        }
    }
}

This is my recreation using PHP that isn’t operating as I would expect:

$quadkey = intval($_GET["quadkey"]);

$zoom = count($quadkey);

for ($i = $zoom; $i > 0; $i--)
{
    $mask = 1 << ($i - 1);

    $quadkey_array = str_split($quadkey);

    switch ($quadkey_array[$zoom - $i])
    {
        case 0:
            break;

        case 1:
            $x |= $mask;
            break;

        case 2:
            $y |= $mask;
            break;

        case 3:
            $x |= $mask;
            $y |= $mask;
            break;

        default:
            echo "Error";
    }


    echo "/" . $zoom . "/" . $x . "/" . $y . ".png";
}

The example quadkey I’m using and the expected results are as follows:

Quadkey: 120202111102203112
X-coord: 134926
Y-coord: 86121
Zoom: 18

Would anyone be able to shed some light on what I’m doing wrong? I’ve been looking all around and can’t find any other example code to examine! Thanks all!

Answer 1

There are mistakes in my code that I should have seen.

$zoom = count($quadkey);

Is wrong and counts the number of $quadkeys, not the length of the string.

$zoom = strlen($quadkey);

Also, the URL should be generated outside of the for loop, just below it. I have placed the updated code below should anyone else need a PHP script for converting a Bing maps quadkey to coordinates.

$quadkey = intval($_GET["quadkey"]);

$zoom = strlen($quadkey);

for ($i = $zoom; $i > 0; $i--)
{
    $mask = 1 << ($i - 1);

    $quadkey_array = str_split($quadkey);

    switch ($quadkey_array[$zoom - $i])
    {
        case 0:
            break;

        case 1:
            $x |= $mask;
            break;

        case 2:
            $y |= $mask;
            break;

        case 3:
            $x |= $mask;
            $y |= $mask;
            break;

        default:
            echo "Error";
    }
}

echo "/" . $zoom . "/" . $x . "/" . $y . ".png";