Royal Mail Barcode Checksum Generator

A PHP Class to Generate a Royal Mail Barcode Checksum, as outlined in [this] guide.

Details on what this requires are as follows;

6.5. Checksum character

If you don?t use proprietary software from PIF or a Royal Mail approved co-supplier then

you?ll need to work out the checksum character yourself.

This involves using an algorithm, as described below. The checksum character is used as a

means of error detection to ensure that the rest of the barcode is correct.

*Working out the checksum character*

Checksum characters can be automatically produced through the software available from

co-suppliers. They are also available on the PIF®. They can however also be calculated by

following these steps:

Step one

Use the table to find row and column references for the characters in the Postcode and DPS.

Note that the sixth row/column is numbered 0 not

| | 1 | 2 | 3 | 4 | 5 | 0 | |-------|-----|-----|-----|-----|-----|-----| | 1 | 0 | 1 | 2 | 3 | 4 | 5 | | 2 | 6 | 7 | 8 | 9 | A | B | | 3 | C | D | E | F | G | H | | 4 | I | J | K | L | M | N | | 5 | O | P | Q | R | S | T | | 0 | U | V | W | X | Y | Z |

For example the letter S is in row 5 and column 5. Write these down in a grid like this (we?ve

used an example Postcode of SN3 4RD and DPS of 1A), then add them up:

|Postcode and DPS | S | N | 3 | 4 | R | D | 1 | A | Total | |-----------------:|---|---|---|---|---|---|---|---|:--------:| | Row | 5 | 4 | 1 | 1 | 5 | 3 | 1 | 2 | 22 | | Column | 5 | 0 | 4 | 5 | 4 | 2 | 2 | 5 | 27 |

Step two

Divide the totals by six (it is always six, no matter how many characters are in the Postcode),

and note the amount left over. In this example:

goes into 22 three times with 4 left over

6 goes into 27 four times with 3 left over

Step three

Refer these ?left over? figures back to the table, finding the character where they intersect.

For example, row 4 and column 3 gives the checksum character K.

Even if your ?left over? character is zero (i.e. 6 into 24 goes four times with zero left over), this

will relate to a row or column on the grid.

General Usage Instructions

In order to use the class. Simply include the file, and create an instance of it in your application.

Then call the ProcessPostcode() Function with the Post Code you require the checksum for.

i.e.

*$chk = new PostCodeCheckSum();*

*$checksum = $chk->ProcessPostcode(?MK1 1ST?);*

[this]: http://onepost.co.uk/wp-content/uploads/2013/03/OP-RM-Appendix-H.pdf