How do i get php to work inside of google maps

Im trying to use google maps to display artist tour dates with points on the map. I have Lat/Lon getting queried in php, There is about 20 results that all have lat/lon. When I plug the values into the google map javascript only one result is showing on the map. What am I doing wrong here?

php

 $lat =  get_field('gp_latitude');
 echo json_encode($lat)."<br>";
 $lon = get_field('gp_longitude');
 echo json_encode($lon)."<br>";
 $infobox = get_the_title();
 echo json_encode($infobox). "<br>";
 $postid = get_the_ID(); 
 echo json_encode($postid). "<br><br>";

javascript

<script type="text/javascript">
          var locations = [
            ['<?php echo json_encode($infobox) ?>', <?php echo json_encode($lat) ?>, <?php echo json_encode($lon) ?>, <?php echo json_encode($postid) ?>, 2],
            ['<?php echo json_encode($infobox) ?>', <?php echo json_encode($lat) ?>, <?php echo json_encode($lon) ?>, <?php echo json_encode($postid) ?>, 1]
      ];

var map = new google.maps.Map(document.getElementById('map'), {
  zoom: 2,
  center: new google.maps.LatLng(-33.92, 151.25),
  mapTypeId: google.maps.MapTypeId.ROADMAP
});

var infowindow = new google.maps.InfoWindow();

var marker, i;

for (i = 0; i < locations.length; i++) {  
  marker = new google.maps.Marker({
    position: new google.maps.LatLng(locations[i][1], locations[i][2]),
    map: map
  });

  google.maps.event.addListener(marker, 'click', (function(marker, i) {
    return function() {
      infowindow.setContent(locations[i][0]);
      infowindow.open(map, marker);
    }
  })(marker, i));
}