# Barcode

`Zend_Validate_Barcode` allows you to check if a given value can be represented as barcode.

`Zend_Validate_Barcode` supports multiple barcode standards and can be extended with proprietary barcode implementations very easily. The following barcode standards are supported:

- CODE25: Often called "two of five" or "Code25 Industrial".

  This barcode has no length limitation. It supports only digits, and the last digit can be an optional checksum which is calculated with modulo 10. This standard is very old and nowadays not often used. Common usecases are within the industry.

- CODE25INTERLEAVED: Often called "Code 2 of 5 Interleaved".

  This standard is a variant of CODE25. It has no length limitation, but it must contain an even amount of characters. It supports only digits, and the last digit can be an optional checksum which is calculated with modulo 10. It is used worldwide and common on the market.

- CODE39: CODE39 is one of the oldest available codes.

  This barcode has a variable length. It supports digits, upper cased alphabetical characters and 7 special characters like whitespace, point and dollar sign. It can have an optional checksum which is calculated with modulo 43. This standard is used worldwide and common within the industry.

- CODE39EXT: CODE39EXT is an extension of CODE39.

  This barcode has the same properties as CODE39. Additionally it allows the usage of all 128 ASCII characters. This standard is used worldwide and common within the industry.

- CODE93: CODE93 is the successor of CODE39.

  This barcode has a variable length. It supports digits, alphabetical characters and 7 special characters. It has an optional checksum which is calculated with modulo 47 and contains 2 characters. This standard produces a denser code than CODE39 and is more secure.

- CODE93EXT: CODE93EXT is an extension of CODE93.

  This barcode has the same properties as CODE93. Additionally it allows the usage of all 128 ASCII characters. This standard is used worldwide and common within the industry.

- EAN2: EAN is the shortcut for "European Article Number".

  These barcode must have 2 characters. It supports only digits and does not have a checksum. This standard is mainly used as addition to EAN13 (ISBN) when printed on books.

- EAN5: EAN is the shortcut for "European Article Number".

  These barcode must have 5 characters. It supports only digits and does not have a checksum. This standard is mainly used as addition to EAN13 (ISBN) when printed on books.

- EAN8: EAN is the shortcut for "European Article Number".

  These barcode can have 7 or 8 characters. It supports only digits. When it has a length of 8 characters it includes a checksum. This standard is used worldwide but has a very limited range. It can be found on small articles where a longer barcode could not be printed.

- EAN12: EAN is the shortcut for "European Article Number".

  This barcode must have a length of 12 characters. It supports only digits, and the last digit is always a checksum which is calculated with modulo 10. This standard is used within the USA and common on the market. It has been superceded by EAN13.

- EAN13: EAN is the shortcut for "European Article Number".

  This barcode must have a length of 13 characters. It supports only digits, and the last digit is always a checksum which is calculated with modulo 10. This standard is used worldwide and common on the market.

- EAN14: EAN is the shortcut for "European Article Number".

  This barcode must have a length of 14 characters. It supports only digits, and the last digit is always a checksum which is calculated with modulo 10. This standard is used worldwide and common on the market. It is the successor for EAN13.

- EAN18: EAN is the shortcut for "European Article Number".

  This barcode must have a length of 18 characters. It support only digits. The last digit is always a checksum digit which is calculated with modulo 10. This code is often used for the identification of shipping containers.

- GTIN12: GTIN is the shortcut for "Global Trade Item Number".

  This barcode uses the same standard as EAN12 and is its successor. It's commonly used within the USA.

- GTIN13: GTIN is the shortcut for "Global Trade Item Number".

  This barcode uses the same standard as EAN13 and is its successor. It is used worldwide by industry.

- GTIN14: GTIN is the shortcut for "Global Trade Item Number".

  This barcode uses the same standard as EAN14 and is its successor. It is used worldwide and common on the market.

- IDENTCODE: Identcode is used by Deutsche Post and DHL. It's an specialized implementation of Code25.

  This barcode must have a length of 12 characters. It supports only digits, and the last digit is always a checksum which is calculated with modulo 10. This standard is mainly used by the companies DP and DHL.

- INTELLIGENTMAIL: Intelligent Mail is a postal barcode.

  This barcode can have a length of 20, 25, 29 or 31 characters. It supports only digits, and contains no checksum. This standard is the successor of PLANET and POSTNET. It is mainly used by the United States Postal Services.

- ISSN: ISSN is the abbreviation for International Standard Serial Number.

  This barcode can have a length of 8 or 13 characters. It supports only digits, and the last digit must be a checksum digit which is calculated with modulo 11. It is used worldwide for printed publications.

- ITF14: ITF14 is the GS1 implementation of an Interleaved Two of Five bar code.

  This barcode is a special variant of Interleaved 2 of 5. It must have a length of 14 characters and is based on GTIN14. It supports only digits, and the last digit must be a checksum digit which is calculated with modulo 10. It is used worldwide and common within the market.

- LEITCODE: Leitcode is used by Deutsche Post and DHL. It's an specialized implementation of Code25.

  This barcode must have a length of 14 characters. It supports only digits, and the last digit is always a checksum which is calculated with modulo 10. This standard is mainly used by the companies DP and DHL.

- PLANET: Planet is the abbreviation for Postal Alpha Numeric Encoding Technique.

  This barcode can have a length of 12 or 14 characters. It supports only digits, and the last digit is always a checksum. This standard is mainly used by the United States Postal Services.

- POSTNET: Postnet is used by the US Postal Service.

  This barcode can have a length of 6, 7, 10 or 12 characters. It supports only digits, and the last digit is always a checksum. This standard is mainly used by the United States Postal Services.

- ROYALMAIL: Royalmail is used by Royal Mail.

  This barcode has no defined length. It supports digits, uppercased letters, and the last digit is always a checksum. This standard is mainly used by Royal Mail for their Cleanmail Service. It is also called RM4SCC.

- SSCC: SSCC is the shortcut for "Serial Shipping Container Code".

  This barcode is a variant of EAN barcode. It must have a length of 18 characters and supports only digits. The last digit must be a checksum digit which is calculated with modulo 10. It is commonly used by the transport industry.

- UPCA: UPC is the shortcut for "Univeral Product Code".

  This barcode preceeded EAN13. It must have a length of 12 characters and supports only digits. The last digit must be a checksum digit which is calculated with modulo 10. It is commonly used within the USA.

- UPCE: UPCE is the short variant from UPCA.

  This barcode is a smaller variant of UPCA. It can have a length of 6, 7 or 8 characters and supports only digits. When the barcode is 8 chars long it includes a checksum which is calculated with modulo 10. It is commonly used with small products where a UPCA barcode would not fit.

## Supported options for Zend_Validate_Barcode

The following options are supported for `Zend_Validate_Barcode`:

- adapter: Sets the barcode adapter which will be used. Supported are all above noted adapters. When using a self defined adapter, then you have to set the complete classname.

- checksum: `TRUE` when the barcode should contain a checksum. The default value depends on the used adapter. Note that some adapters don't allow to set this option.

- options: Defines optional options for a self written adapters.

## Basic usage

To validate if a given string is a barcode you just need to know its type. See the following example for an EAN13 barcode:

    $valid = new Zend_Validate_Barcode('EAN13');
    if ($valid->isValid($input)) {
        // input appears to be valid
    } else {
        // input is invalid
    }

## Optional checksum

Some barcodes can be provided with an optional checksum. These barcodes would be valid even without checksum. Still, when you provide a checksum, then you should also validate it. By default, these barcode types perform no checksum validation. By using the checksum option you can define if the checksum will be validated or ignored.

    $valid = new Zend_Validate_Barcode(array(
        'adapter'  => 'EAN13',
        'checksum' => false,
    ));
    if ($valid->isValid($input)) {
        // input appears to be valid
    } else {
        // input is invalid
    }

### Reduced security by disabling checksum validation

By switching off checksum validation you will also reduce the security of the used barcodes. Additionally you should note that you can also turn off the checksum validation for those barcode types which must contain a checksum value. Barcodes which would not be valid could then be returned as valid even if they are not.

## Writing custom adapters

You may write custom barcode validators for usage with `Zend_Validate_Barcode`; this is often necessary when dealing with proprietary barcode types. To write your own barcode validator, you need the following information.

- Length: The length your barcode must have. It can have one of the following values:

  - Integer: A value greater 0, which means that the barcode must have this length.

  - -1: There is no limitation for the length of this barcode.

  - "even": The length of this barcode must have a even amount of digits.

  - "odd": The length of this barcode must have a odd amount of digits.

  - array: An array of integer values. The length of this barcode must have one of the set array values.

- Characters: A string which contains all allowed characters for this barcode. Also the integer value 128 is allowed, which means the first 128 characters of the ASCII table.

- Checksum: A string which will be used as callback for a method which does the checksum validation.

Your custom barcode validator must extend `Zend_Validate_Barcode_AdapterAbstract` or implement Zend_Validate_Barcode_AdapterInterface.

As an example, let's create a validator that expects an even number of characters that include all digits and the letters 'ABCDE', and which requires a checksum.

    class My_Barcode_MyBar extends Zend_Validate_Barcode_AdapterAbstract
    {
        protected $_length     = 'even';
        protected $_characters = '0123456789ABCDE';
        protected $_checksum   = '_mod66';

        protected function _mod66($barcode)
        {
            // do some validations and return a boolean
        }
    }

    $valid = new Zend_Validate_Barcode('My_Barcode_MyBar');
    if ($valid->isValid($input)) {
        // input appears to be valid
    } else {
        // input is invalid
    }