The communication between the merchant’s system/customer’s browser, to the gateway Payment Form are POST via HTML form variables. The below table or similar format, is used throughout this document to help explain the requirements for passing/receiving variables to/from the gateway.

An example HTML form POST variable which would get to the gateway;
<input type=”hidden” name=”InputName” value=”InputValue” />

Input Field Name	Data Type	Max Length	Mandatory or Always Present	Comments
Input Name

Input Field Name:

The value in this field is case sensitive and should be sent exactly as is stated here. Failure to do so will result in errors, specifically relating to missing variables or hash digest mismatches.

Data Type:

All variables will be converted to a string when the HTML is rendered anyway, but, this is to stipulate what the expected value should be readable as. For example, Boolean should only be sent as “TRUE” or “FALSE”. Some scripting languages like PHP only state “1” or “0” for Boolean, which would be deemed invalid by the gateway so all values must be converted to the noted data type first.

Max Length:

This is the maximum length that the gateway will allow for the variable. If a “-“ is noted, this means it is of variable length. If there is a numerical value in the field, any variables passed that are longer than this will result in an error.

Mandatory:

This informs the merchant if a variable is deemed to be mandatory by the gateway. Failure to send mandatory variables to the gateway will result in an error. If this is marked with “Yes”, check the comments section also as there may be specific situations when it is not mandatory.

Comments:

This field should be read thoroughly to determine if they are relevant to the integration you are performing. This field may contain information explaining more in depth the variables use and/or assist in determining if it is indeed mandatory or not.