1. Set the domain form action to example.com/domainchecker.php
2. You need to create another input type whose name will be "domain" and value should be the domain name which your client passes.
For example:
<input type="text" name="domain" value="example.com"> The type can be hidden or text.
3. You need to create another input type hidden whose value will be registered, in case of transfer the value will be transfer.
For example:
<input type="hidden" name="name" value="register">
<form action="example.com/domainchecker.php" method="post">
<input type="hidden" name="name" value="register">
<input type="text" name="domain">
<input type="submit" value="search">
</form>
