如何在PHP和JavaScript之间进行通信

Question

I wrote a JavaScript function to convert GeoJson data to WKT format. It works when i get the input value in the javascript code directly. But I don't know how to get the input from the php and send it back.

Here is the php code:

<?php
  $geojson=file_get_contents("clipfeature.geojson");
  $WKT = $_POST['wkt'];
  echo ($WKT);
?>

So it gets geojson data from a file and I want to receive the converted WKT code from the Javascript function.

Please help me finish the JavaScript Code:

   function converttoWKT (){
     $.ajax({
        type: "GET",
        url: "readJson.php",
        contentType: "application/json"
    }).done(function (data) {

    var JSONObject = How to give the value from PHP to this Variable;

    var coordinate = JSONObject.features[0].geometry.coordinates;
    var type= JSONObject.features[0].geometry.type;


    var coordinate1 = "";
    var coordinate2 = "";
    for (var i=0; i< coordinate[0].length; i++) {
     coordinate1= coordinate[0][i][0]+" "+coordinate[0][i][1];
     coordinate2=coordinate1+","+coordinate2;
    }

    var WKT= "\""+ type + "((" + coordinate2;
        WKT=WKT.substring(0,WKT.length-1);
        WKT=WKT+"))\"" 

    sendback ( );

}); 

    function sendback(){$.post("readJson.php",
    {'wkt':How to send the value of var WKT back to php 'wkt'
    });
    }

Answer 1

Basically:

var jsVar= "<? echo $myVariable_value_goes_in_here; ?>";

or, as mentioned above:

var JSONObject =  <? echo json_encode($WKT); ?>;  
                  // this NEED TO BE json, otherwise syntax error in JS!

Answer 2

Since you already know your return data will be JSON, you can just use $.getJSON() for convenience. This is a $.get() request paired with JSON.parse() . With $.getJSON() , the JSON is parsed on response. To send the data back, just use use jQuery's $.post() .

Here's an edited version of your code.

function converttoWKT() {
  $.getJSON('clipfeature.geojson', function(data) {
    var coordinate = data.features[0].geometry.coordinates;
    var type = data.features[0].geometry.type;

    var coordinate1 = '';
    var coordinate2 = '';
    for(var i = 0; i < coordinate[0].length; i++) {
      coordinate1 = coordinate[0][i][0] + ' ' + coordinate[0][i][1];
      coordinate2 = coordinate1 + ',' + coordinate2;
    }

    var WKT = '"' + type + '((' + coordinate2;
    WKT = WKT.substring(0, WKT.length - 1);
    WKT = WKT + '))"'

    sendback(WKT);
  });
};

function sendback(data) {
  $.post('readJson.php', {
    'wkt': data
  });
};