Put a JSON facade on top of of Hampton Roads Transit Data

hrtrtf.php

<?php

// FTP URI to transit data.
define("TRANSIT_FTP_URI", "ftp://216.54.15.3/Anrd/hrtrtf.txt");

// Parse a string and return specific element.
function parseString($string, $num) {
  $pieces = explode("  ", trim($string));
  return $pieces[$num];
}

// Get the transit data.
$data = file_get_contents(TRANSIT_FTP_URI);
$rows = explode("\n", $data);

// An array to hold vehicle locations.
$positons = array();

// Iterate over each record in the file and parse out vehicle info.
foreach($rows as $row) {

  $record = explode("   ", $row);
  $type = parseString($record[0], 3);
  $vehicle_id = parseString($record[0], 1);
  
  if($type == "MT_LOCATION") {
    $coordinates = parseString($record[1], 0);
  }
  else {
    $coordinates = parseString($record[1], 8);
  }
  // Assumes a specific level of precision.
  $lat = substr($coordinates, (strpos($coordinates, ':')+1), 9); 
  $lon =  substr($coordinates, (strpos($coordinates, '/-')+1), 9); ;
  
  array_push($positons, array("type" => $type, "id" => $vehicle_id, "lat" => $lat, "lon" => $lon));
  
}

// Make some JSON and return it.
$positions_json = json_encode($positons);
header('Content-type: applicaiton/json');
echo $positions_json;

?>