Maybe it's my lack of sleep, but I don't even see any kind of input box in your code at all.
Input boxes are part of the HTML <form> set. To create an input box that has any relevance, you must put it in a form that is set to some kind of action. Here's an example:
<form method="post" action="/cgi/php/process_form.php">
Please enter the amount you want:
<input type="text" name="Donation_Amount" />
<br />
</form>
When a person types in the amount and hits <Enter>, this will redirect the user to a processing script called process_form.php . Also, you could add a button if you wanted, but in this example it is superfluous.
The only way that I know of PHP creating an input text box is through echoing or printing the appropriate HTML commands to the screen.
Hope this helps.