由提交按钮触发的下拉列表过滤器

我已经制作了一个过滤器功能，但是我在使用起始表时遇到问题，如果没有为过滤器选择类别，我希望显示从表中选择的所有数据。到目前为止，我可以显示选择类别所需的所有必要数据，但前提是选择类别。如果未选择任何选项，则会显示一个空白表。请帮忙,...

这是函数

 function listhistoryHost(){
    $accountid=$_SESSION['userid'];
    if(isset($_POST['button'])){
    $filter=$_POST['historyfilter'];
    if($filter==$filter){
    $sql="select * from webhostrequest where status='$filter' order by webhostrequest.recentact desc";
    $result=mysql_query($sql) or die("Error in selecting items ".mysql_error());
        $out="<ul>";
            while($row=mysql_fetch_array($result)){
                $accountid=$row['userid'];
                $requesttitle=$row['requesttitle'];
                $requestid=$row['requestid'];
                echo "<table width='"100%'" border='"0'" cellpadding='"2'">";
                echo "<tr class='"rowcolor1'">";
                    echo "<td width='"70%'"><span style='"padding-left:20px'">Requested Web Hosting for  ".$row["requesttitle"]. "</td>";
                    echo "<td width='"20%'"><span style='"padding-left:20px'">Status: " .$row["status"]. "</td>";
                    echo "<td>
                    <center>
                        <form id = '"form1'" method = '"post'" action = '"viewhistorywebhost.php?webhost=$requestid'">
                            <input type = '"submit'" name = '"button'" id = '"button'" value = '"Details'" />
                        </form>
                    </center>";
                echo "</tr>";   
            }
            echo "</table>";
    return $out;
    }
    }
    }

这是表单和触发器

 <form id = "form1" method = "post" action = "#">
        <select id="select1" name="historyfilter">
        <option value='' selected disabled>Select item type</option>
            <?php
                $options = array('approved' => 'Approved',
                                'cancelled'=>'Cancelled',
                                'rejected' => 'Rejected');
                foreach($options as $value => $type){
                    echo "<option value='"$value'">$type</option>";
                }
            ?>
        </select>   
            <input type = "submit" name = "button" id = "submit" value = "Go" />
        </form>
    <?php
        $webhost=new requisition2();
        echo $webhost->listhistoryHost();
    ?>