I have records with lat and lngs in a MySQL database and I want to add them to a Leaflet map as markers. I have tried a couple of methods but none seem to work. When the webpage opens the map doesn't show up and I get "ReferenceError: Incidents is not defined" in the console.

Here is my php file (get.php)

$username = 'aname'; 
$password = 'apassword; 
$host = 'localhost'; 
$dbname = 'adb';

// open the database
try {
    $db = new PDO("mysql:host=$host;dbname=$dbname", $username, $password);
} catch(PDOException $e) {
    // send the PDOException message

try {
    $sql="SELECT protocol,jurisdiction,date,time,comments,video,lat,lng FROM Incidents";
    $stmt = $db->prepare($sql);
} catch(PDOException $e) {
    print "db error ".$e->getCode()." ".$e->getMessage();

$ajxres=array(); // place to store the geojson result
$features=array(); // array to build up the feature collection

// go through the list adding each one to the array to be returned   
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {





// add the features array to the end of the ajxres array
// tidy up the DB
$db = null;
sendajax($ajxres); // no return from there

function sendajax($ajx) {
    // encode the ajx array as json and return it.
    $encoded = json_encode($ajx);

EDIT: Here is my JavaScript (pd_map.js):

var map;
var centerlatlng = L.latLng(35.85199,-119.6577);

var southWest = L.latLng(3.3,-154.2),
northEast = L.latLng(61.5,-58.4),
bounds = L.latLngBounds(southWest, northEast);

var myIcon1 = L.icon({
iconUrl: 'http://www.broomfield.org/images/pages    /N315/blue%20heading%20icons_building.png',
iconSize: [30, 30]

var red = L.icon({
iconUrl: 'img/red.png',
iconSize: [30, 30]

$(document).ready(function (){

// Creating a tile layer using ESRI - World Physical Map
var aLayerOne = L.tileLayer('http://services.arcgisonline.com/arcgis /rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}.png', {
                maxZoom: 19


// Creating a tile layer using MapBox
var aLayerTwo = L.tileLayer('http://api.tiles.mapbox.com /v4/davidjbailey.jg612ji1/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoiZGF2aWRqYmFpbGV5IiwiYSI6InFxSzA5bjgifQ.tDw01mG43kf6hWUIAtBEAw#4/33.75/-117.87', {
                attribution: 'Developed <a href="">DB</a>',
                maxZoom: 18

// Creating a geojson layer using geojson file
// You can set the style using Leaflet Path Class - http://leafletjs.com/reference.html#path

// Cities
var aLayerThree = L.geoJson(aGeoJson1,  {
                    pointToLayer: function (feature, latlng) {
                        return L.marker(latlng,{icon: myIcon1});
                    }, // end of point to layer{

                    onEachFeature: function(feature, layer){

                        layer.on('load', function(e){
                        }); //  event functio                    

                        layer.on('click', function(e){
                            map.setView([e.latlng.lat, e.latlng.lng], 11);
                            aDiv.innerHTML = "<center>" + "<strong>Welcome to </strong>" + "<strong>" + feature.properties.name + "!" + "</strong>" + "<br>" + "<h5>" + "Explore the data by zooming in" + "<br>" +
                            "and out and by clicking on points." + "</h5>" + "------------"  + "<h5>" + "Add an incident to the map by clicking on the" +
                            "<br>" + "marker symbol in the upper left corner of the map." + "</h5>" + "</center>"
                        }); //  event function

                        layer.on('mouseover', function(e){                          
                            aDiv.innerHTML = "<strong>" + feature.properties.name + "</strong>"

                            }); // End of mouseover event function
                        layer.on('mouseout', function(e){                           
                            aDiv.innerHTML = "<strong>Click on your city!</strong>"   



//Create our Map Object
            map = L.map('myMap', {
                        center: centerlatlng,
                        zoom:   6,
                        maxBounds: bounds,
                        minZoom: 4,
                        maxZoom: 18,

                        layers: [aLayerThree, aLayerTwo]

UserMarker = L.featureGroup().addTo(map);

L.drawLocal.draw.toolbar.buttons.marker = 'Add an incident to the map!';

var drawControl = new L.Control.Draw({
draw: {
polygon: false,
polyline: false,
rectangle: false,
                icon: red 
circle: false,

edit: {
featureGroup: UserMarker

map.on('draw:created', function (e) {
 var type = e.layerType,
    layer = e.layer;
    var coords = e.layer._latlng;
 var popup = L.popup({maxWidth: 1400})
    .setContent('<form role="form" id="form" enctype="multipart/form-data" onsubmit="addMarker()">'+

             '<div class="form-group">'+
              '<label class="control-label col-sm-10"><strong>Was the person following protocol?</strong></label>'+ "<br>" +
              '<input type="text" placeholder="Yes, No, or I dont know" id="protocol" name="protocol" class="form-control"/>'+ 

             '<div class="form-group">'+
              '<label class="control-label col-sm-10"><strong>Jurisdiction </strong></label>'+ "<br>" +
              '<input type="text" placeholder="City, State, County, or Other" id="jurisdiction" name="jurisdiction" class="form-control"/>'+ 

           '<div class="form-group">'+
              '<label class="control-label col-sm-10"><strong>Date </strong></label>'+ "<br>" +
              '<input type="text" placeholder="8/1/2015" id="date" name="date" class="form-control"/>'+ 

          '<div class="form-group">'+
              '<label class="control-label col-sm-10"><strong>Time of day </strong> </label>'+ "<br>" +
              '<input type="text" placeholder="Morning, Afternoon, or Night" id="time" name="time" class="form-control"/>'+ 

          '<div class="form-group">'+
              '<label class="control-label col-sm-10"><strong>Comments </strong></label>'+ "<br>" +
              '<input type="text" placeholder="Briefly tell us what happened" id="comments" name="comments" class="form-control"/>'+ 

          '<div class="form-group">'+
              '<label class="control-label col-sm-10"><strong>Video Link </strong></label>'+ "<br>" +
              '<input type="text" placeholder="Do you have a video? Add link here" id="video" name="video" class="form-control"/>'+ 

          '<input style="display: none;" type="text" id="lat" name="lat" value="'+coords.lat.toFixed(6)+'" />'+
          '<input style="display: none;" type="text" id="lng" name="lng" value="'+coords.lng.toFixed(6)+'" />'+

          '<div class="form-group">'+
                '<div style="text-align:center;" class="col-xs-11"><button style="text-align:center;" type="submit" id="submit" value="submit" class="btn btn-primary trigger-submit">Submit</button></div>'+
          '</div>'+ "<br>" +

        '<strong>' + '-' + '</strong'+



        $('#submit').click(function(e) {

        //do your own request an handle the results
                url: 'submit.php',
                type: 'post',
                dataType: 'json',
                data: $("#form").serialize(),
                complete: function(data) {
              window.location = "Map_member1.php"




//Adding a Scale Control

    //adding a Layer Control
var baseLayers = {
    "Satellite imagery": aLayerOne,
    "Streets": aLayerTwo

// create a variable holding the overlays
var overLays  = {
'Cities': aLayerThree,


function askForIndidents() {
        url: 'get.php',
        dataType: 'json',
        data: data,
        success: showIncidents

function showIncidents(ajxresponse) {
    lyr = L.geoJson(ajxresponse, {onEachFeature: makePopup})

L.control.layers(baseLayers, overLays, {collapsed: false}).addTo(map);

    $(document).ready(function() {
    $('#myMap').css('height', ($(window).height() - 50));

  $(window).resize(function () {
    $('#myMap').css('height', ($(window).height() - 50));

    ///Creating custom control here
// part 1/3 : Creates a control with the given position
var aControl = L.control({position: 'bottomright'});

// part 2/3 : Should contain code that creates all the neccessary DOM elements for the control
aControl.onAdd = function () {

        aDiv = L.DomUtil.create('div', 'aCustomC'); // create a div with a class "aCustomC"
        aDiv.innerHTML = "<strong>Click on your city!</strong>" // Each HTML element has an innerHTML property that defines both the HTML code and the text that occurs between that element's opening and closing tag.

                    return aDiv;
}; // end function onAdd

// part 3/3 : Add the control to the map

    // create the geocoding control and add it to the map
  var searchControl = new L.esri.Controls.Geosearch({useMapBounds: 8}).addTo(map);

  // create an empty layer group to store the results and add it to the map
  var results = new L.LayerGroup().addTo(map);

  // listen for the results event and add every result to the map
  searchControl.on("results", function(data){
  for (var i = data.results.length - 1; i >= 0; i--) {


});// end document ready

I am new to this and I'm hoping someone can help me in the right direction!


2 Answers 2


See code example Leaflet users map https://github.com/bmcbride/leaflet-users-map by Bryan McBride. There is used SQLite DB, but her easy replace on MySQL.

  • This helped a lot. I'm able to add my data (markers) from mySQL to Leaflet with this. However the L.MarkerClusterGroup is not working but that's for another discussion
    – Djb
    Sep 4, 2015 at 17:30

Your code:

Wont work because 'Incidents' isn't defined yet (hence your error message). Try running it without the 'Incidents' in here.

Or drop your code into this section:

function showIncidents(ajxresponse) {

Something like this:

function showIncidents(ajxresponse) {
    // Incidents geojson layer
    lyr = L.geoJson(ajxresponse, {
        onEachFeature: makePopup

That might work. You're doing a lot at once, and it's a little unclear where it might go wrong!

You can have a look at one of my examples here, which uses ajax to display GeoJSON data: https://github.com/gccgisteam/maps-website/blob/master/graffiti.html

It's a little complex, but you should be able to generalise it from there.

  • I did what you said (see edits) and the map now shows up with no error but the markers (from mySQL) are still not showing up on the map. Does my Ajax requests look correct? i'll take a more in depth look at your graffiti project
    – Djb
    Sep 3, 2015 at 6:37
  • Load your project in Chrome and insert a breakpoint. Then check the data your PHP script is returning. developer.chrome.com/devtools/docs/javascript-debugging
    – Alex Leith
    Sep 3, 2015 at 6:53
  • @AlexLeith, are you sure his actual error is client-side? ..I copy/pasted the JS code into Notepad++ and did CTRL+F against "Incidents" and got 0 matches ..which means the variable "Incidents" is not in his client-side code in the first place. For the browser to throw a reference error on a variable named "Incidents" ..shouldn't it be in the code somewhere? Maybe in a different file not mentioned in the post?
    – elrobis
    Sep 3, 2015 at 16:43
  • Hi @elrobis, he changed his code after my answer. Doing interactive debugging in Chrome and inspecting the data returned from server-side will allow him to work out where the issue is.
    – Alex Leith
    Sep 4, 2015 at 21:36

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