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Passing data into leaflet js via a php script

General Tech Bugs & Fixes 2 years ago

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Posted on 16 Aug 2022, this text provides information on Bugs & Fixes related to General Tech. Please note that while accuracy is prioritized, the data presented might not be entirely correct or up-to-date. This information is offered for general knowledge and informational purposes only, and should not be considered as a substitute for professional advice.

Answers (2)

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manpreet Tuteehub forum best answer Best Answer 2 years ago

 

I'm trying to display route data on a map using leaflet. I'm pulling the data from a MYSQL database with a php script. which is working. The data is stored in an array called vechiclelatlong. I use  under the Javascript tag where is have my Leaflet script. I am getting the following error:

Uncaught ReferenceError: vehiclelatlong is not defined

See scripts below:

PHP script:

<php   
function vData(){   
include("dbconnecti.php");

$strtDate = strtotime('20150404');
$endDate = strtotime('20150405');

$query = "SELECT ED.latitude, ED.longitude, ED.timestamp, ED.creationTime 
FROM EventData ED 
WHERE ED.latitude <> 0 AND ED.longitude <> 0 AND (ED.timestamp >= $strtDate)  AND (ED.timestamp <= $endDate)";
$results = $dbconnect->query($query);

if (!$results)  {
    echo mysql_error();
    die('There was an error excuting query statment: ' ); //. mysqli_error());
}

$num_of_rows = $results -> num_rows;
$data = array();

echo "var vehiclelatlong = [";

for ($x = 0; $x < $num_of_rows; $x++)   {
    $data[] = $results -> fetch_assoc();

    echo "[".$data[$x]['latitude'].",".$data[$x]['longitude']."]";
    if ($x <= $num_of_rows - 2)  
    {
        echo ",";
    }
  }

  echo "];";

}
vData();
?>

HTML script

 DOCTYPE html>   
 <html>    
 <head>    
    <title>Tobago Street Map title>
    <link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/black-tie/jquery-ui.css" type="text/css" /> 
    <script type="text/javascript" src="http://code.jquery.com/jquery-latest.js" charset="utf-8">script>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/jquery-ui.min.js" charset="utf-8">script>
    <link rel=
                                                

                                                                                                        
                                                    
                                                

                                                

                                                    

                                                        
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manpreet 2 years ago

While your PHP looks to be creating an array, I'm not sure that you're going to have consistent luck getting JS to read it that way (an arrant space here or there, etc.). At least I've tried that in the past, only to realize that while it LOOKS like a good array, it isn't.

I think you're better off just returning your MySQL as a true array and then using json_encode($array) to get it in something that will consistently be read by JS.

Something like

var vehiclelatlong = php json_encode($array); ?>;

EDIT: Lets stick with your array (although JSON ~ GEOJSON and there are good PHP GEO tools out there). I got it to work doing the following.
1. made sure both files had a *.php extension
2. removed **" on either side of my include statement in my main page
3. made sure my included file was correctly referenced in my main page
4. made sure my DB query was returning a valid result. I made some changes (including just trying it using SQLite) but you can see the same result.

php   
function vData(){  
$db = new PDO("sqlite:so.db");
$query = "SELECT latitude, longitude FROM EventData";
$statement1 = $db->prepare($query);
$statement1->execute();
$results = $statement1->fetchall(PDO::FETCH_ASSOC);
echo "var vehiclelatlong = [";
$count=1;
foreach ($results as $result)   {
echo "[".$result['latitude'].",".$result['longitude']."]";
if ($count < count($results)) echo ",";
$count++;
}
echo "];";
}
vData();
?>

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