Typically, the way you do that is to redisplay a clean form right after your PHP code to do the insert like this:
<?php
if ($_REQUEST['submit'] {
// put your code here for processing the submit of a form
}
?>
<!-- Now display a clean form -->
<form action="thispage.php">
<input type=text name=field1>
<input type=submit value="Go" name="submit">
</form>
That way, everytime you submit the page, it goes to itself, processes the form data, and displays another form.
If this is being designed for someone at your company to be able to enter lots of records, I find that it's easier to have them open a program like Excel or a text editor and have them enter the data there and save it as a CSV file. Then you write a program to do batch imports from a CSV. That way, you can have them do their data entry in a page where they can have tools like cut and paste, spell check, etc.