why are arabic numbers (١٢٣) not accepted in textboxes as real numbers?

AFAIK you need to install an arabic language pack with ./mage install - see http://www.magentocommerce.com/magento-connect/Ahmed+J.+Hadi/extension/353/magento-community-modules--arabic-saudi-arabia-language-pack

To allow PHP to accept the Arabic numbers or Persian numbers (Farsi) (١٢٣٤٥), I developed this easy function:

<?php

/*
/////////////////////
This function has been created by Abdulfattah alhazmi
Roles:
To convert Arabic/Farsi Numbers (٠‎ - ١‎ - ٢‎ - ٣‎ - ٤‎ - ٥‎ - ٦‎ - ٧‎ - ٨‎ - ٩‎) 
TO the corrosponding English numbers (0-1-2-3-4-5-6-7-8-9)
http://hazmi.co.cc
/////////////////////
*/

function convertArabicNumbers($arabic) {
    $trans = array(
        "&#1632;" => "0",
        "&#1633;" => "1",
        "&#1634;" => "2",
        "&#1635;" => "3",
        "&#1636;" => "4",
        "&#1637;" => "5",
        "&#1638;" => "6",
        "&#1639;" => "7",
        "&#1640;" => "8",
        "&#1641;" => "9",
    );
    return strtr($arabic, $trans);
}
?>

Note: TO GET THE CORRECT RESULT from text field in your form, you have to use the htmlspecialchars_decode() function. For example:

$mytext = htmlspecialchars_decode($_POST['mytext']));
$mytext = convertArabicNumbers($mytext);

To keep your code safe, add strip_tags(). For example:

$mytext = strip_tags(htmlspecialchars_decode($_POST['mytext']));
$mytext = convertArabicNumbers($mytext);

Please don't hesitate to ask me if you have any further question about this function.