Retaining input from previous form to new form

Question

I'm guessing this is the link that you are clicking and need to it to pass on values?

echo "<a href='insertnewquotation.php'><input type='button' class='button' value='Add New Items' /></a>";

It's simply a matter of appending query string variables to the URL so that the insertnewquotation.php file receives them like:

echo "<a href='insertnewquotation.php?name=$cust_name&producttype=$product_type...'

Then in the insertnewquotation.php you can retrieve them with something like:

$cust_name = isset( $_GET['cust_name'] ) ? $_GET['cust_name'] : "";

Hope that points you in the right direction.

Note: I won't even touch the usage of deprecated mysql_* functions since this is a school project.

EDIT

In your input, you have to assign the value attribute and use PHP tags where appropriate:

<?php
   // Get Customer Name and Filter
   $custName = isset( $_GET['cust_name'] ) ? strip_tags($_GET['cust_name']) : "";
?>
<input name="custname" 
       type="text" 
       value="<?php echo($custName); ?>">

NOTE: It is generally not a good idea to use raw query variables before filtering. In this case it is not that problematic, but never ever use raw query string data in a database query. That's just asking for SQL Injection.