<div class="col-lg-4 col-md-4 col-sm-4 col-xs-12"></div>
<div class="col-lg-4 col-md-4 col-sm-6 col-xs-12">
<div class="panel panel-default">
<div class="panel-body">
<div class="panel-heading"><h3>Calculation = <?php
echo $cal->sum();
?>
</h3></div>
<form role="form">
<div class="form-group">
<label for="val1">Value 1</label>
<input type="number" name="val1" class="form-control" placeholder=" Enter number">
</div>
<select class="form-control" name="operator">
<?php
$cal->get_Operator();
?>
</select>
<div class="form-group">
<label for="val2">Value 2</label>
<input type="number" name="val2" class="form-control" placeholder=" Enter number">
</div>
<button type="submit" name="calculate" value="Calculate" class="btn btn-success">Calculate</button>
</form>
</div>
</div>
</div>
</div>
</div>
</body>
</html>
