CODEWITHSUNDEEP
phppostgresqlgeojson
user1344766
user1344766

Reputation: 93

parse GeoJson String in PHP

I want to get polygon coordinates from below String.

{"polygon":{"type":"Feature","properties":[],"geometry":{"type":"Polygon","coordinates":[[[-7302732.4720101,6527844.6333235],[-3193477.8319711,6606116.1502766],[-5111129.9973226,5001550.0527375],[-6637424.5779086,4884142.7773079],[-7772361.5737289,5158093.0866438],[-7302732.4720101,6527844.6333235]]]},"crs":{"type":"name","properties":{"name":"urn:ogc:def:crs:OGC:1.3:CRS84"}}}}

This is GeoJson string that i decode to array with below code: 

$polygon = CJSON::decode($str);

when i want to get polygon i get error! 

$var= $polygon->polygon;

or with below code:

$polygon = CJSON::decode($str,true);
$var = $polygon['polygon'];

although for getting coordinates:

foreach($polygon as $key=>$value)
$coordinates = $value['coordinates'];
or
$coordinates = $value[coordinates];

how can i get coordinates from geojson that i send from javascript to php for saving on postgresql with postgis?

Upvotes: 2

Views: 6162

Answers (2)

chris
chris

Reputation: 36937

$polygon->polygon->geometry->coordinates[0]

or

$polygon['polygon']['geometry']['coordinates'][0]

what you have is a multidimensional array/object not sure which its being output to when decoded in your case as it appears you have a class doing it I would have just used json_decode, but anyway. Yea from the looks of it, polygon is the main object, then in it is geometry which is an object that has type and coordinates, and then coordinates has multiple objects/arrays in it.

the above samples if I typed them right will show the first set of coordinates in that object. Of course you could run it through a loop ie:

In the case that it is an object assuming your Class decodes as an object and not an array. Not exactly sure what $polygon = CJSON::decode($str,true); does. But if its anything like json_decode() then you should be all set.

This is my method of breaking down the object as you present here, its worth noting you may want to check counts, and see if the object is set first, or if the property exists in the object to prevent other means of the code breaking down the road. But what I have here is just pure example at its core, it will server its purpose though. But will not error handle which is why I say you may want to elaborate further on it doing those checks.

Anyway heres my code:

<?php
$str = '{"polygon":{"type":"Feature","properties":[],"geometry":{"type":"Polygon","coordinates":[[[-7302732.4720101,6527844.6333235],[-3193477.8319711,6606116.1502766],[-5111129.9973226,5001550.0527375],[-6637424.5779086,4884142.7773079],[-7772361.5737289,5158093.0866438],[-7302732.4720101,6527844.6333235]]]},"crs":{"type":"name","properties":{"name":"urn:ogc:def:crs:OGC:1.3:CRS84"}}}}';

$polygon = json_decode($str);
echo'<pre>';print_r($polygon);echo'</pre>';

$set = 1;
foreach($polygon->polygon->geometry->coordinates[0] as $coordinates)
{
    echo 'Set '.$set.': ';$set++;
    echo $coordinates[0].','.$coordinates[1].'<br>';
}
?>

see it in action http://7pz.net/geojson-parse.php (scroll to the bottom)

Upvotes: 2

Gga
Gga

Reputation: 4421

This should give you an array of all the coordinates and print them out line by line:

$string = '{"polygon":{"type":"Feature","properties":[],"geometry":{"type":"Polygon","coordinates":[[[-7302732.4720101,6527844.6333235],[-3193477.8319711,6606116.1502766],[-5111129.9973226,5001550.0527375],[-6637424.5779086,4884142.7773079],[-7772361.5737289,5158093.0866438],[-7302732.4720101,6527844.6333235]]]},"crs":{"type":"name","properties":{"name":"urn:ogc:def:crs:OGC:1.3:CRS84"}}}}';

$json = json_decode($string);

$coords_array = $json->polygon->geometry->coordinates[0];

foreach($coords_array as $c_a) {
        echo $c_a[0] . "," .$c_a[1] . "<br>"; 
    }

Access with:

$coords_array[0];
$coords_array[1];
$coords_array[2];

etc.

Basically you can turn the JSON string into an object and access each element with the -> notation.

I usally use a site called http://jsonviewer.stack.hu/ to decode JSON and find the path I need, then simply write them out as they appear, as in as in the above - $json->polygon->geometry->coordinates;.

Try it out yourself on the site.

Upvotes: 1

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