php 안 함수 호출 질문

<div id="doc_zone"><!-- 문서 상세내역 --> </div>

<form method="post">

            <tr>

                <th><?php echo $i+1; ?></th>              

                <td><input type="text" class="td_center" name="doc_sub" value="<?php echo $list[$i]['doc_sub']; ?>" id="doc_sub" readonly>

                <td><input type="text" class="td_center" name="doc_size" value="<?php echo $list[$i]['doc_size']; ?>" id="doc_size" readonly>

                <td><input type="text" class="td_center" name="doc_ea" value="<?php echo $list[$i]['doc_ea']; ?>" id="doc_ea" readonly>

                <td><input type="text" class="td_center" name="doc_cnt" value="<?php echo number_format($list[$i]['doc_cnt']); ?>" id="doc_cnt" readonly>

                <td><input type="text" class="td_center" name="doc_use" value="<?php echo $list[$i]['doc_use']; ?>" id="doc_use" readonly>

                <td><input type="text" class="td_center" name="doc_reason" value="<?php echo $list[$i]['doc_reason']; ?>" id="doc_reason" readonly>

                <?php if($list[$i]['doc_1'] == "0|0"){?>

                <!-- 전송완료시 판별할 값 만들어야함 g5_write_purchase_sub 칼럼생성  doc_1 2022.01.03-->

                <td><input class="btn_b02 btn" type="submit"  name="bb" id="bb" value="전송"></td>

                <?php }?>

            </tr>

            </form>

            <?php

            function insert(){

                header("Refresh:0");

                }

                if(array_key_exists('bb',$_POST)){

                insert();

            }

            ?>