Forms that dont refresh the page

Ive seen that there are forms that dont reset the page using jquery. however im not well versed in it and am still not 100% comfortable with jquery so my brain usually goes on the rampage trying to figure it out any other way. If i have a very small div with maybe position set to top:-20px; left:-20px; and in that div was a small iframe. If i submit my form to the iframe then the page doesnt reset. I dont neccisarily need for information to be passed back to the page with the form on it so my question is... is this a valid method? what are the pros and cons of it.

HTML Code:

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<form name="mine" action="testf.php" method="post" target="subbers">
<input name="quantity" type="text" value="1" required="required" /><input name="addcart" type="submit" value="submit" />
</form>
<iframe name="subbers" src="blank.php" width="2" height="2" style="position:absolute; top:-20px; left: -20px;"></iframe>

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testf.php

PHP Code:

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<?php
echo "welcome to this page<br>";
$quantity = $_POST['quantity'];
echo "you have selected ".$quantity." items";
?>

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