Get itinerary latitudes & longitude from google maps with PHP - php

Question

I want to list the latitude and longitude of itinerary. It could be all points or it could be all points in 1-2 kilometers.
What I'm trying to do is: user selected A as the starting point and B as the ending point. I want to show some places near the road between A and B on the map. But I need a positions for this.
As an example, a JavaScript code is shared here and It is said that this can be done with DirectionsResult Object.
var request = {
origin: start_point,
destination: end_point,
travelMode: google.maps.TravelMode.DRIVING
};
var directionsService = new google.maps.DirectionsService();
directionsService.route(request, function(response, status) {
if (status == google.maps.DirectionsStatus.OK) {
var path = (response.routes[0].overview_path);
}
});
But I'm trying to do this with php and I have to do this with php.
I read google map api. I've also read the yandex map api, but this seems to be done only with javascript.
Does anyone know a way to do this with php?

Answer 1

From comments I understand the question is to find (using PHP) the intermediate lat,lng pairs that can be extracted from the polyline points in a google directions query.
This is a bit unusual because people normally use the polyline points for map drawing in the browser, and so the JavaScript libraries are well equipped for this task. However, not so in PHP.
The points data appears in the JSON result object as string of ascii characters, sometimes quite long and always 'unreadable'. Into this string is encoded a list of intermediate lat lng pairs between the start and end of each leg. The coding method is presented at the google site https://developers.google.com/maps/documentation/utilities/polylinealgorithm and the algorithm below is just a reversal of that and is commented accordingly.
The example shows a directions find between 2 points, on crescent shaped streets, in Perth, Australia. The start-end points were chosen to encourage multiple intermediate points as would be needed to draw the route. Substitute your own search as needed.
Note that the JSON also provides these fields also at the end of each results object.
"overview_polyline" : {
"points" : "~n{aEmbwaU_B#cCBk#Lo#d#UVOb#Mh#Ab####BBF#DGNABD`#Fh#Pb#VZn#b#d#J"
},
This is much less detailed and less accurate (if you draw will probably depart from actual road lines on map), but can also be decoded in the same way.
The best intermediate points are however, by iterating through the steps using:
"polyline" : {
"points" : "~n{aEmbwaUg##w#?{A?g#BUBUHSJ[XUVOb#Mh#Ab#"
},
Finally, the original source for the algorithm can be found here http://unitstep.net/blog/2008/08/02/decoding-google-maps-encoded-polylines-using-php/. So thanks to Peter Chng for this work back in 2008! Peter also acknowledges Mark MClure who did the original coding in JavaScript. I hacked about with and added more comments - to make more aligned with the google recipe, but no more.
I have also just realised there is this link https://github.com/emcconville/google-map-polyline-encoding-tool which (I think but have not tested) provides a class and a CLI tool to do the conversions both ways.
$json = file_get_contents("https://maps.googleapis.com/maps/api/directions/json?origin=20%20%20Kintyre%20Crescent,%20Churchlands&destination=%2018Kinross%20Crescent,%20Churchlands&key=");
$details = json_decode($json,true);
print_r($details); // show the full result
$points = $details['routes'][0]['legs'][0]['steps'][0]['polyline']['points'];
echo($points); // show the points string for one leg
// show the start and end locations for that leg
print_r($details['routes'][0]['legs'][0]['steps'][0]['start_location']);
print_r($details['routes'][0]['legs'][0]['steps'][0]['end_location']);
// work out the intermdiate points (normally used for drawing)
$decodedPoints= decodePolylinePoints($points);
print_r($decodedPoints); // print out the intermediate points
// This function decodes the polylone points in PHP
function decodePolylinePoints($pointsString)
{
$len = strlen($pointsString);
$latLons = array(); // the output array
$lat = 0; // temp storage for lat and lng
$lng = 0;
$index = 0; // index to curent character
while ($index < $len) // process each lat,lng pair
{
// first build the lat
// NOTE: first lat is an absolute value
// NOTE: subsequent lats are offsets from previous values for coding efficiency
$char = 0; // char as read from points string
$shift = 0; // cumulative shift amount
$value = 0; // temp value during computation
do // Read, convert and shift 5 bit chunks until terminator is reached to get lat
{
$char = ord(substr($pointsString, $index++)) - 63; // return ascii value less 63
$value |= ($char & 0x1f) << $shift; // convert to 5 bit and shift left
$shift += 5; // next shift is 5 extra
}
while ($char >= 0x20); // value of 20 indicates end of lat
$lat += (($value & 1) ? ~($value >> 1) : ($value >> 1)); // convert negative values and save
// now build the lng
// NOTE: first lng is an absolute value
// NOTE: subsequent lngs are offsets from previous values for coding efficiency
$shift = 0;
$value = 0;
do // build up lng from 5 bit chunks
{
$char= ord(substr($pointsString, $index++)) - 63; // return ascii value less 63
$value |= ($char & 0x1f) << $shift; // convert to 5 bit and shift left
$shift += 5; // next shift is 5 extra
}
while ($char >= 0x20); // value of 20 indicates end of lng
$lng += (($value & 1) ? ~($value >> 1) : ($value >> 1)); // convert negative values and save
$latLons[] = array($lat * 1e-5, $lng * 1e-5); // original values were * 1e5
}
return $latLons; // points array converted to lat,lngs
}