(PHP + JS) GOOGLE MAPS API V3 Missing Markers Problem?

p开发者_运维百科hp noobie here. Would like to seek the help of you guys on the following codes for Google Maps.

I have this javascript that works perfectly fine in plotting the markers. However, there lies a problem where the marker numbers seems to jump. (instead of 1,2,3,4 it jumps like 1,4,5,7). The following are my javascript codes which does the plotting of markers:

<script>
function initialize() {
    var centerMap = <?php echo json_encode($locations[0]) ?>;
    var centerMap2 = <?php echo json_encode($locations2[0]) ?>;
    var locations = <?php echo json_encode($locations) ?>;
    var locations2 = <?php echo json_encode($locations2) ?>;
    var centerLatlng = new google.maps.LatLng(centerMap, centerMap2);
    var map = new google.maps.Map(document.getElementById("map_canvas"), {
        zoom: 2,
        center: centerLatlng,
        mapTypeId: google.maps.MapTypeId.ROADMAP,
    });

    var marker, i, image, count;

    for (i = 0; i < locations.length; i++) {  

    image = new google.maps.MarkerImage('markers/marker'+i+'.png');


        marker = new google.maps.Marker({
            position: new google.maps.LatLng(locations[i], locations2[i]),
            icon: image,
            map: map
        });

    }

}
</script> 

Could this be a problem where similar co-ordinates are in place which results in the markers replacing each other?

thanks for any kind advices given! :)