PHP表单提交错误显示不成功

I created this form with PHP and MySQL. Whenever I submit the form and click update button it is showing unsucess. I don't know what is going wrong and I need help finding the problem. I've attached the code below.

<?php
error_reporting(E_ALL & ~E_NOTICE);
error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED); 

$con = mysqli_connect("localhost","root","") or die("unable to connect");

mysqli_select_db($con,'studentdb');

if(isset($_GET['registernumber']))

    $registernumber = html_entity_decode($_GET['registernumber']);

    $query= "SELECT * FROM studenttble WHERE registernumber='$registernumber'";

                $query_run = mysqli_query($con,$query);


                while($row = mysqli_fetch_array($query_run, MYSQL_ASSOC))
                {
                    $IID = $row['IID'];
                    $studentname = $row['studentname'];
                    $fathername = $row['fathername'];
                    $registernumber = $row['registernumber'];
                    $year = $row['$year'];
                    $dept = $row['$dept'];
                    $section = $row['section'];
                    $gender = $row['gender'];
                    $password = $row['password'];
                    $email = $row['email'];
                    $dob = $row['dob'];
                    $raddress = $row['raddress'];
                    $mnumber = $row['mnumber'];

                }
    ?>          
<form action="<?php $_SERVER['PHP_SELF'] ?>" method="post" id="form1" class="myform">
  <table align="center">
    <tr>
      <td>
        <input name="estudentname" type="text" id="studentname" class="wp-form-control wpcf7-text" value="<?php echo $studentname?>" />
      </td>
    </tr>
    <br>
    <tr>
      <td>
        <input name="efathername" type="text" id="fathername" class="wp-form-control wpcf7-text" value="<?php echo $fathername?>" />
      </td>
    </tr>
    <tr>
      <td>
        <input type="hidden" name="registernumber" id="registernumber" class="wp-form-control wpcf7-text" value="<?php echo $registernumber?>" placeholder="Register Number" />
      </td>
    </tr>
    <tr>
      <td>
        <input type="text" name="egender" id="gender" class="wp-form-control wpcf7-text" value="<?php echo $gender?>" />
      </td>
    </tr>
    <tr>
      <td><input type="text" name="eemail" type="email" id="email" class="wp-form-control wpcf7-text" value="<?php echo $email?>" />

      </td>
    </tr>
    <tr>
      <td>
        <h3 class="table">Date Of Birth:  &nbsp; &nbsp;<input  type="text"  name="edob" id="dob" type="date" class="dropdown-menu-left" value="<?php echo $dob?>"  max="2017-02-08"/></td></tr>
</h3>
        <tr>
          <td> &nbsp; &nbsp; <input type="text" class="wp-form-control wpcf7-textarea" name="eraddress" cols="30" rows="10" value="<?php echo $raddress?>"></textarea>
          </td>
        </tr>
        <tr>
          <td> <input name="emnumber" type="text" id="mnumber" pattern="[789][0-9]{9}" class="wp-form-control wpcf7-text" max="10" value="<?php echo $mnumber?>" />
          </td>
        </tr>

        <tr>
          <td align="center">
            <input type="submit" name="update" class="wpcf7-submit" value="update"> &nbsp; &nbsp;
          </td>
        </tr>
  </table>
</form>


<?php
  if(isset($_POST['update'])) 
  {
    $con = mysqli_connect("localhost","root","") or die("unable to connect");
    mysqli_select_db($con,'studentdb');

    $estudentname = mysql_real_escape_string($_POST['estudentname']);
    $efathername = mysql_real_escape_string($_POST['efathername']);
    $egender = mysql_real_escape_string($_POST['egender']);
    $eemail = mysql_real_escape_string($_POST['eemail']);
    $edob = mysql_real_escape_string($_POST['edob']);
    $eraddress = mysql_real_escape_string($_POST['eraddress']);
    $emnumber = mysql_real_escape_string($_POST['emnumber']);
    $targetid = mysqli_real_escape_string($_POST['registernumber']);

    mysqli_select_db('studentdb');
    $query = "UPDATE studenttble SET studentname ='$estudentname', fathername ='$efathername', gender ='$egender', email ='$eemail', dob ='$edob', raddress ='$eraddress', mnumber ='$emnumber' WHERE registernumber ='$targetid'";

    $retval = mysqli_query( $query, $conn );

    if($retval)
    {
        echo "sucess";
    }
    else
    {
        echo "unsucess";
    }
  }

?>