Select and Update data from database mysql in php

<?php include db_config.php ?>
<table width="100%" border="1">
        <tr> 
          <td><strong><font color="#000000">Application No.</font></strong></td>
          <td><strong><font color="#000000">Investor Name</font></strong></td>
          <td><strong><font color="#000000">Gender</font></strong></td>
          <td><strong><font color="#000000">Occuptionn</font></strong></td>
          <td><strong><font color="#000000">National ID</font></strong></td>
          <td><strong><font color="#000000">Mobil</font></strong></td>
          <td><strong><font color="#000000">Phone</font></strong></td>
          <td><strong><font color="#000000">Email</font></strong></td>
        </tr>


 <?PHP
    $db=new mysqli(SERVER,USER,PASSWORD,DATABASE);
	$sql="select * from dealer";
	$rs = $db->query($sql);
    while ($row = $rs->fetch_array(MYSQL_ASSOC)) {    
    ?>
        <tr> 
         	<td><?php echo $row['Application']; ?></td>
            <td><?php echo $row['Investor']; ?></td>
            <td><?php echo $row['Gender']; ?></td>
            <td><?php echo $row['Occuption']; ?></td>
            <td><?php echo $row['NidNo']; ?></td>
            <td><?php echo $row['Mobil']; ?></td>
            <td><?php echo $row['Phone']; ?></td>
            <td><?php echo $row['Email']; ?></td>
     		<td><a href="edit_dealer.php?id=<?php echo $row['id']; ?>"><strong>Edit</strong></a></td>
        </tr>

 <?php
  }
  ?>

  </table>

<?php include db_config.php ?>
$Id=$_GET["id"];
$db=new mysqli(SERVER,USER,PASSWORD,DATABASE);
$sql1="select id,Appdate,Application,Investor from dealer where id='$Id'";
$rs = $db->query($sql1);
$row = $rs->fetch_row();
 	
  	$Appdate =$row[0];
	$Application=$row[1];
	$Investor=$row[2];
	$FatherName=$row[3];
	$MotherName=$row[4];

if(isset($_POST["btnSubmit"])){
	
	$Appdate =$_POST["Appdate"];
	$Application=$_POST["txtApplication"];
	$Investor=$_POST["txtInvestor"];
	$FatherName=$_POST["txtFatherName"];
	$MotherName=$_POST["txtMotherName"];

	$err="";

if($err==""){
	$db=new mysqli(SERVER,USER,PASSWORD,DATABASE);
	
	$sql="update dealer set Appdate='$Appdate',Application='$Application',Investor='$Investor',FatherName='$FatherName',MotherName='$MotherName' where id='$Id'";
		
	$rs=$db->query($sql);
	}else{
		echo "<font color='red'><h4>$err</h4></font>"	;
	}
}
?>

<form action="#" method="post">
<table>
	<tr>
    	<td>ID</td>
        <td><input type="text" name="txtId" value="<?php echo $Id? $Id:''?>" readonly style="background-color:#dddddd;" /></td>       
    </tr>
	<tr>
    	<td>Date</td>
        <td><input type="date" name="Appdate" value="<?php echo $Appdate? $Appdate:''?>"/></td>       
    </tr>
    <tr>
    	<td>Application No.</td>
        <td><input type="text" id="txtApplication" name="txtApplication"  value="<?php echo $Application? $Application:''?>"/></td>
    </tr>
	<tr>
    	<td>Name of Investor</td>
        <td><input type="text" id="txtInvestor" name="txtInvestor" value="<?php echo $Investor? $Investor:''?>" /></td>
    </tr>
    <tr>
    	<td>Father's Name</td>
        <td><input type="text" id="txtFatherName" name="txtFatherName" value="<?php echo $FatherName? $FatherName:''?>" /></td>
    </tr>
     <tr>
    	<td>Mother's Name</td>
        <td><input type="text" id="txtMotherName" name="txtMotherName" value="<?php echo $MotherName? $MotherName:''?>" /></td>
    </tr>
</table>
</form>