nicebooks/isbn

ISBN tools

0.6.1 2026-01-20 23:33 UTC

Requires

• php: ^8.2

Requires (Dev)

• ext-dom: *
• brick/varexporter: ~0.5.0
• carthage-software/mago: 1.0.3
• php-coveralls/php-coveralls: ^2.5.2
• phpunit/phpunit: ^11.5

MIT

• book
• ISBN
• ISBN-10
• ISBN-13
• books
• Nicebooks

README

This library provides functionality for validating, formatting, and converting ISBN numbers. It powers the nicebooks.com website and is available for use under the permissive MIT open-source license.

ISBN validation and formatting follow the rules defined by the ISBN range file published by the International ISBN Agency.

Installation

This library is installable via Composer:

composer require nicebooks/isbn

Requirements

The current version of this library requires PHP 8.2 or higher.

You may use earlier versions of nicebooks/isbn with earlier versions of PHP, but you will only receive ISBN range updates if you use the latest version.

Project status & release process

While this library is still under development, it is well tested and should be stable enough to use in production environments. It is currently in use in production on nicebooks.com.

The current releases are numbered 0.x.y. When a non-breaking change is introduced (updating ISBN ranges, adding new methods, optimizing existing code, etc.), y is incremented.

When a breaking change is introduced, a new 0.x version cycle is always started.

It is therefore safe to lock your project to a given release cycle, such as 0.6.*.

If you need to upgrade to a newer release cycle, check the release history for a list of changes introduced by each further 0.x.0 version.

Overview

The Isbn class

The Isbn class is an abstract, immutable class representing an ISBN-10 or ISBN-13 with a valid format and a valid check digit.

It has 2 subclasses: Isbn10 and Isbn13, allowing for narrower typing if your application expects only ISBN-10 or only ISBN-13 at some point.

An Isbn instance is obtained with the of() factory method:

use Nicebooks\Isbn\Isbn;

$isbn = Isbn::of('123456789X'); // will return an instance of Isbn10
$isbn = Isbn::of('9781234567897'); // will return an instance of Isbn13

You can also use the Isbn10::of() and Isbn13::of() factory methods, which will attempt to convert the given ISBN to the corresponding subclass:

Isbn10::of('123456789X'); // equivalent to Isbn::of('123456789X')->to10();
Isbn13::of('9781234567897'); // equivalent to Isbn::of('9781234567897')->to13();

If the given string does not have a valid format or check digit, an InvalidIsbnException is thrown.

Note

Before validation, the provided string is stripped of all non-alphanumeric ASCII characters.

Checking the type of an ISBN

You can check the type of an ISBN with the is10() and is13() methods:

Isbn::of('123456789X')->is10(); // true
Isbn::of('123456789X')->is13(); // false

Isbn::of('9781234567897')->is10(); // false
Isbn::of('9781234567897')->is13(); // true

You can also use instanceof checks:

Isbn::of('123456789X') instanceof Isbn10; // true
Isbn::of('9781234567897') instanceof Isbn13; // true

Converting between ISBN-10 and ISBN-13

An ISBN-10 can be converted to an ISBN-13 with the to13() method:

Isbn::of('123456789X')->to13(); // Isbn13 instance with value 9781234567897

An ISBN-13 can be converted to an ISBN-10 with the to10() method:

Isbn::of('9781234567897')->to10(); // Isbn10 instance with value 123456789X

Only ISBN-13 numbers starting with 978 can be converted to ISBN-10. You can check if an ISBN can be converted to an ISBN-10 with the isConvertibleTo10() method:

Isbn::of('9781234567897')->isConvertibleTo10(); // true
Isbn::of('9791234567896')->isConvertibleTo10(); // false

If you call to10() on an ISBN-13 that does not start with 978, an IsbnNotConvertibleException is thrown.

Comparing ISBN numbers

You can compare two Isbn instances with the isEqualTo() method. An ISBN-10 can be compared to an ISBN-13, and the comparison will be successful if both numbers resolve to the same ISBN-13 number:

Isbn::of('123456789X')->isEqualTo(Isbn::of('9781234567897')); // true

Validating an ISBN

While an Isbn instance is guaranteed to have a valid format and a valid check digit, it may not belong to a valid range according to the range file published by the International ISBN Agency.

The Isbn class provides two methods to further validate an ISBN:

Method	Description
hasValidRegistrationGroup()	Only checks if the ISBN belongs to a known registration group.
isValid()	Checks if the ISBN belongs to a known registration group and a known range. This is the highest level of validation that can be performed by looking at the ISBN number alone.

Note

Which ISBNs are considered valid depends on the library version you are using. This library is kept in sync with the ISBN ranges published by the International ISBN Agency, so keep it up to date for proper validation.

Formatting an ISBN

The library provides two methods to format an ISBN:

Method	Description	ISBN-10 example	ISBN-13 example
toString()	Returns the unformatted ISBN	133887893X	9781338878936
toFormattedString()	Returns the formatted ISBN if the ISBN is valid, otherwise returns the unformatted number	1-338-87893-X	978-1-338-87893-6

Splitting an ISBN into parts

An ISBN-13 is divided into 5 parts:

978-1-338-87893-6
——— — ——— ————— —
 A  B  C    D   E

While an ISBN-10 is divided into 4 parts:

1-338-87893-X
— ——— ————— —
B  C    D   E

The Isbn class provides getters for each part:

Part	Example	Description	Getter
A	978	Prefix	getRegistrationGroup()->prefix
B	1	Registration group identifier	getRegistrationGroup()->identifier
C	338	Publisher identifier (registrant)	getPublisherIdentifier()
D	87893	Title identifier (publication)	getTitleIdentifier()
E	6	Check digit	getCheckDigit()

Important

• Parts A and B require hasValidRegistrationGroup() (or isValid(), which implies it)
• Parts C and D require isValid()

You can also get the ISBN parts as an array:

Isbn::of('9781338878936')->getParts(); // ['978', '1', '338', '87893', '6']

Important

getParts() requires isValid()

If the part you're trying to access is not available because the ISBN does not belong to a valid registration group or range, an IsbnException is thrown.

Getting the registration group name

getRegistrationGroup() also exposes the group's name:

Isbn::of('9781338878936')->getRegistrationGroup()->name; // 'English language'

Exceptions

Exceptions live in the Nicebooks\Isbn\Exception namespace.

• IsbnException is the base class for all exceptions thrown by this library.
  • InvalidIsbnException is thrown when an invalid ISBN is detected
  • IsbnNotConvertibleException is thrown when trying to convert an ISBN-13 that does not start with 978 to an ISBN-10.