Weird error when updating database using php - php

Question

I have a weird problem in which if I delete the line Type doctor name <input type="text" name="new_Doctor_name" value="<?php echo $row1[3]; ?>" ><br />, I cannot update my records and get the notice Undefined variable: row1. However, if I keep this line, which I copy from another table, I can update just fine.
Please explain this. Any help will be highly appreciated.
<?php
include_once('Connect.php');
if( isset($_GET['edit1']) )
{
$id = $_GET['edit1'];
$res1= mysql_query("SELECT * FROM department WHERE Dept_name='$id'");
$row1= mysql_fetch_array($res1);
}
if( isset($_POST['new_Doctor_name']) )
{
$id = $_POST['id'];
$new_Dept_name = $_POST['new_Dept_name'];
$new_Ward = $_POST['new_Ward'];
$sql1 = "UPDATE department SET Dept_name='$new_Dept_name', Ward='$new_Ward' WHERE Dept_id='$id'";
$res2 = mysql_query($sql1) or die("Could not Update".mysql_error());
echo "<meta http-equiv='refresh' content='0;url=Department_viewtable.php'>";
}
var_dump($row1);
?>
<FORM ACTION="Department_dmod.php" METHOD="post">
<input type="hidden" name="id" value="<?php echo $id; ?>" />
***Type doctor name <input type="text" name="new_Doctor_name" value="<?php echo $row1[3]; ?>" ><br />***
Type Department Name <input type="text" name="new_Dept_name" value="<?php echo $row1[1]; ?>" ><br />
Type Department Ward <input type="text" name="new_Ward" value="<?php echo $row1[2]; ?>" >
<INPUT TYPE="SUBMIT" NAME="UPDATE" VALUE="UPDATE">
<p><a href=Department_viewtable.php>Back to the Department table</a></p>
<p><a href=Main_Menu.php>Back to Main menu</a></p>
</FORM>

Answer 1

The if() statement :
if( isset($_POST['new_Doctor_name']) )
Will only ever be executed if an input element exists in the POST data with a name of new_Doctor_name. If you remove it from the DOM, it will not be passed with the request, and thus the queries won't execute.
It may be better to check for the presence of the UPDATE variable inside the POST request:
if(isset($_POST['UPDATE']))
{
$id = $_POST['id'];
$new_Dept_name = $_POST['new_Dept_name'];
$new_Ward = $_POST['new_Ward'];
$sql1 = "UPDATE department SET Dept_name='$new_Dept_name', Ward='$new_Ward' WHERE Dept_id='$id'";
$res2 = mysql_query($sql1) or die("Could not Update".mysql_error());
echo "<meta http-equiv='refresh' content='0;url=Department_viewtable.php'>";
}
It's also worth noting that the mysql_* family of functions is now deprecated. Instead, you should look at MySQLi or PDO. Finally, your code is open to SQL injection, so I'd recommend looking at Prepared Statements, too.

Answer 2

The variable row1 is set in this part of the code. If the variable is returning an error that it has not been defined this means that the code below has not been executed. This code is only ran if the $_GET['edit1'] variable is set.
if( isset($_GET['edit1']) )
{
$id = $_GET['edit1'];
$res1= mysql_query("SELECT * FROM department WHERE Dept_name='$id'");
$row1= mysql_fetch_array($res1);
}