credit es FLOAT y price viene del siguiente formulario:
Código:
<form name="pg_frm" method="post" action="http://www.paygol.com/micropayment/paynow_post" >
<input type="text" name="pg_custom" value="UserID">
<input type="hidden" name="pg_serviceid" value="XXXX">
<input type="hidden" name="pg_currency" value="EUR">
<input type="hidden" name="pg_name" value="Comprar Creditos">
<!-- With Dropdown -->
<select name="pg_price">
<option value="1" selected>100</option>
<option value="2">200</option>
<option value="3">300</option>
</select>
<input type="hidden" name="pg_return_url" value="http://www.miweb.com">
<input type="hidden" name="pg_cancel_url" value="">
<input type="image" name="pg_button" class="paygol" src="http://www.paygol.com/micropayment/img/buttons/150/pay_es_3.png" border="0" alt="Realiza pagos con PayGol: la forma mas facil!" title="Realiza pagos con PayGol: la forma mas facil!" onClick="pg_reDirect(this.form)">
</form>
No funciona creando la variable $credit, vere poniendo el (int) o cambiando la tabla a integer.