问PHP / MySQL:多次删除时出错，仅删除了最新的ID

EN

    <?php

    include("configPDO.php");

    $smt = $conn->prepare("SELECT * FROM frame_list ORDER BY framework_name ASC");
    $smt->execute();
    $results = $smt->fetchAll();


    ?>

<form method="post" id="multiple_select_form">
    <select name="framework[]" id="framework" class="form-control selectpicker" data-live-search="true" multiple>
        <?php foreach ($results as $row2): ?>
            <option value= <?php echo $row2["framework_id"]; ?>><?php echo $row2["framework_name"];?></option>
        <?php endforeach ?>
    </select>
<br><br>
<input type="hidden" name="framework_id" id="framework_id" />
<input type="submit" name="submit" class="btn btn-info" value="Submit" />
</form>

   <script>

    $(document).ready(function(){
    $('.selectpicker').selectpicker();

    $('#framework').change(function(){
    $('#framework_id').val($('#framework').val());
    });

    $('#multiple_select_form').on('submit', function(event){
    event.preventDefault();
    if($('#framework').val() != '')
    {
    var form_data = $(this).serialize();
    $.ajax({
        url:"delete.php",
        method:"POST",
        data:form_data,
        success:function(data)
        {
        //console.log(data);
        $('#framework_id').val('');
        $('.selectpicker').selectpicker('val', '');
        alert(data);
        }
    })
    }
    else
    {
    alert("Please select framework");
    return false;
    }
    });
    });


    </script>

    <?php

    include("configPDO.php");

    $smt = $conn->prepare("DELETE FROM frame_list WHERE framework_id = '".$_POST["framework_id"]."'");
    $smt->execute();

    if($smt){

        echo "Data DELETED";
    }else{
        echo "Error";
    }


    ?>