Transform value of PHP form on submit - php

Question

i'm setting up donate option on a website using przelewy24.pl. They have this startup template to send values by $_GET method to their website.
Everything works fine exept the amount field. Przelewy24 needs a gr amount (like cents) and i would like for the donor to type in integer in full zł (like $).
If the upper is not clear - when i type 100 in the field, it sends it to przelewy24 as 100 gr, whitch will be 1 zł.
I need to know how could i format the amount sent to them as in simple calculation - when 100 is typed, get sends 10000. (x*100)
The form used is shown below. The quick-start guide is avaliable here, but only in polish
<form method="get" action="https://sklep.przelewy24.pl/zakup.php">
<input type="hidden" name="z24_id_sprzedawcy" value="TWOJ_ID">
<input type="hidden" name="z24_crc" value="KLUCZ_ZAKUPU">
<input type="hidden" name="z24_return_url" value="TWOJASTRONA.PL">
<input type="hidden" name="z24_language" value="pl">
<table>
<tr>
<td align="right">Nazwa produktu:</td>
<td>
<input type="text" name="z24_nazwa" value="Opłata za rezerwację NR: 04/234/A3953">
</td>
</tr>
<tr>
<td align="right">Dodatkowy opis:</td>
<td>
<textarea name="z24_opis" style="width:250px">Dodatkowe informacje...
</textarea>
</td>
</tr>
<tr>
<td align="right">Do zapłaty:</td>
<td><input type="text" name="z24_kwota"></td><!--KWOTA W GROSZACH-->
</tr>
</table>
<input type="submit" value="zapłać z przelewy24.pl">
</form>

Answer 1

You can do it with a simple Javascript code.
You need to capture the value from input, transform it, and put the value on input hidden:
function formatMoney(e) {
document.getElementById('z24_kwota').value = (!isNaN(e.target.value) ? e.target.value : 0) * 100
// just to debug.. you can remove this line:
document.getElementById('final_value').innerHTML = document.getElementById('z24_kwota').value
}
<form method="get" action="https://sklep.przelewy24.pl/zakup.php">
<input type="hidden" name="z24_id_sprzedawcy" value="TWOJ_ID">
<input type="hidden" name="z24_crc" value="KLUCZ_ZAKUPU">
<input type="hidden" name="z24_return_url" value="TWOJASTRONA.PL">
<input type="hidden" name="z24_language" value="pl">
<table>
<tr>
<td align="right">Nazwa produktu:</td>
<td>
<input type="text" name="z24_nazwa" value="Opłata za rezerwację NR: 04/234/A3953">
</td>
</tr>
<tr>
<td align="right">Dodatkowy opis:</td>
<td>
<textarea name="z24_opis" style="width:250px">Dodatkowe informacje...
</textarea>
</td>
</tr>
<tr>
<td align="right">Do zapłaty:</td>
<td>
<input type="hidden" name="z24_kwota" id="z24_kwota">
<input type="text" onkeyup="formatMoney(event)"></td><!--KWOTA W GROSZACH-->
</tr>
</table>
<input type="submit" value="zapłać z przelewy24.pl">
</form>
<!-- you can remove this line: -->
Final Value: <span id="final_value"></span>

Answer 2

Try changing the value before submitting the form like below,
<form method="get" id="myform" action="https://sklep.przelewy24.pl/zakup.php">
<input type="hidden" name="z24_id_sprzedawcy" value="TWOJ_ID">
<input type="hidden" name="z24_crc" value="KLUCZ_ZAKUPU">
<input type="hidden" name="z24_return_url" value="TWOJASTRONA.PL">
<input type="hidden" name="z24_language" value="pl">
<table>
<tr>
<td align="right">Nazwa produktu:</td>
<td>
<input type="text" name="z24_nazwa" value="Opłata za rezerwację NR: 04/234/A3953">
</td>
</tr>
<tr>
<td align="right">Dodatkowy opis:</td>
<td>
<textarea name="z24_opis" style="width:250px">Dodatkowe informacje...
</textarea>
</td>
</tr>
<tr>
<td align="right">Do zapłaty:</td>
<td><input type="text" name="z24_kwota"></td><!--KWOTA W GROSZACH-->
</tr>
</table>
<input type="submit" value="zapłać z przelewy24.pl">
</form>
<script
src="http://code.jquery.com/jquery-3.3.1.min.js"
integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8="
crossorigin="anonymous"></script>
<script type="text/javascript">
var firstSubmit = false;
$('#myform').on('submit',function(e){
if(!firstSubmit){
e.preventDefault();
firstSubmit = true;
var amount = parseInt($('input[name=z24_kwota]').val());
$('input[name=z24_kwota]').val(amount*100);
$('#myform').trigger('submit');
}
})
</script>
Note: I have given an id to the form as myform