How to Communicate between PHP and JavaScript - php

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
});
};