Joomla 3分机 我亲爱的

This is my full error:

Warning: Invalid argument supplied for foreach() in C:\xampp\htdocs\bilzar\components\com_blank\views\default\tmpl\default.php on line 14

My code is:

<?php
// Valid execution check
defined('_JEXEC') or die('Restricted Access');
?>
<h1>Blank Component</h1>
<input type="button" class="measure" value="Get New Measurement" />
<table id="thedata">
    <thead>
        <tr>
            <th>Measurement</th><th>Timestamp</th>
        </tr>
    </thead>
    <tbody class="measurements">
        <?php foreach($this -> data as $data) : ?>
            <?php
            $unixTime = strtotime($data->timestamp);
            ?>
        <tr>
            <td><?php echo $data->measurement; ?></td><td><?php echo date("d-m-Y H:i:s", $unixTime); ?></td>
        </tr>
        <?php endforeach; ?>
    </tbody>
</table>
<div class="pagination"><?php echo $this->pagination->getPagesLinks(); ?></div>
<script>

    window.addEvent('domready', function() {

        $$(".measure").addEvent('click', function() {
            var request = new Request.JSON(
            {
                url: 'http://localapache.dyndns.org/joomla_arduino/index.php/blank/sense/sense/raw',
                onSuccess: function(e) {
                    var tr = new Element('tr', {html: '<td>'+e.measurement+'</td><td>'+e.timestamp+'</td>'});
                    var element = $('thedata').getElement('tbody');
                    tr.inject(element, 'top');
                }
        }).get();
        });
        /*

        */
    });

</script>
<style>
    table td { padding: 5px; }

    input[type=button] { margin:10px 0;}

    .pagination ul { list-style-type:none; }
    .pagination ul li { float:left; }
</style>

Can anyone help me how I can fix this error?