ขอความช่วยเหลือ มีพี่คนไหนพอจะช่วยแนะนำ-สอนอ่านโค๊ด php ตัวนี้ผมหน่อยครับ

$brand=null;

###################Insert Section###############
if(isset($_POST['b']['insert'])){//if define b['insert'] inset data
    $b = $_POST['b'];
    $sqli = "INSERT INTO brand(brand)
                VALUE('".$b['brand']."')";
    $rsi = $conn->query($sqli);
    if($rsi){
        $_SESSION['flash']['type']='success';
        $_SESSION['flash']['msg']='เพิ่มข้อมูลเรียบร้อย';
    }else{
        $_SESSION['flash']['type']='danger';
        $_SESSION['flash']['msg']='ไม่สามารถเพิ่มข้อมูลได้';
    }

}

###################Edit Section#################
if(isset($_GET['eid'])){ //if select to Edit
    $bid = $_GET['eid'];

    $sqle = "SELECT * FROM brand WHERE id='".$bid."'";
    $resulte = $conn->query($sqle);
    $rse = mysqli_fetch_array($resulte);

    $brand = $rse['brand'];
   
}

if(isset($_POST['b']['edit'])){// if post data to edit
    $b = $_POST['b'];
    $sqlu = "UPDATE brand SET
            brand='".$b['brand']."'
   
            WHERE id='".$b['id']."'";
    $rsu = $conn->query($sqlu);
    if($rsu){
        $_SESSION['flash']['type']='success';
        $_SESSION['flash']['msg']='แก้ไขข้อมูลเรียบร้อย';
    }else{
        $_SESSION['flash']['type']='danger';
        $_SESSION['flash']['msg']='ไม่สามารถแก้ไขข้อมูลได้';
    }
}

###################Delete Section###############
if(isset($_GET['did'])){
    $sqld = "DELETE FROM brand WHERE id='".$_GET['did']."'";
    $rsd = $conn->query($sqld);
    if($rsd){
        $_SESSION['flash']['type']='success';
        $_SESSION['flash']['msg']='ลบข้อมูลเรียบร้อยแล้ว';
    }else{
        $_SESSION['flash']['type']='danger';
        $_SESSION['flash']['msg']='ไม่สามารถลบข้อมูลได้';
    }
}

###################Select Data Section###############
$sql = "SELECT * FROM brand ORDER BY id DESC";
$result = $conn->query($sql);
?>

<!-- ###############Flash Message############# -->
<?php if(isset($_SESSION['flash'])){ ?>
<div class="alert alert-<?php echo $_SESSION['flash']['type'];?>">
    <?php echo ucfirst($_SESSION['flash']['type']).' '.$_SESSION['flash']['msg'];?>
</div>
<?php }?>
<!--################Insert form############## -->
<div class="row">
<div class="col-md-12">
<h3>ยี่ห้อสินค้า</h3>
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>" class="form-horizontal">
<?php if(isset($_GET['eid'])){?>
    <input type="hidden" name="b[edit]" value="1">
    <input type="hidden" name="b[id]" value="<?php echo $bid;?>">
<?php }else{?>
    <input type="hidden" name="b[insert]" value="1">
<?php }?>
    <div class="form-group">
                <label class="control-label col-md-2" for="b-brand">ยี่ห้อ</label>
                <div class="col-md-10">
                <input id="b-brand" class="form-control" type="text" name="b[brand]" value="<?php echo $brand;?>" required="required">
                </div>

            </div>
        <input type="submit" value="บันทึกข้อมูล ยี่ห้อสินค้า" class="btn btn-primary">
        <?php if(isset($_GET['eid'])){ //if select to Edit ?>
        <a href="admin_brand.php" class="btn btn-warning">ยกเลิก</a>
        <?php }?>

</form>
</div>

<hr />
<div class="col-md-12">
<!-- ###############List of Data############# -->
<h3>รายการยี่ห้อสินค้า</h3>
<table class="table table-bordered table-hover">
    <tr>
        <th>ยี่ห้อ</th>
   
        <th></th>
    </tr>
    <?php while($rs=mysqli_fetch_array($result)){?>
    <tr>
        <td><?php echo $rs['brand'];?></td>
   
        <td>
        <a href="<?php echo $_SERVER['PHP_SELF'];?>?eid=<?php echo $rs['id'];?>" class="btn btn-sm btn-warning">แก้ไข</a>
        <a href="<?php echo $_SERVER['PHP_SELF'];?>?did=<?php echo $rs['id'];?>" class="btn btn-sm btn-danger" onclick="return confirm('แน่ใจนะว่าต้องการลบ?');">ลบ</a>
        </td>
    </tr>
    <?php }?>
</table>
</div>
</div><!--row-->