For parsing, validating and creating HTML doctype strings (in PHP)
, (*1)
Tested against PHP 5.6, 7, 7.1 and 7.2., (*2)
Have you ever found yourself thinking:, (*3)
- My life would be easier if I could programmatically create a doctype string
- I'd be happier if I could parse a doctype string into its component parts
- How can I get a doctype string from a HTML document?
- Is this doctype string that I'm staring at valid?
- I really need get the FPI and URI from this document string and I just don't know how!
Does that apply to you? If so, my goodness are you in luck., (*4)
<?php
use webignition\HtmlDocumentType\Factory;
use webignition\HtmlDocumentType\HtmlDocumentType;
use webignition\HtmlDocumentType\HtmlDocumentTypeInterface;
$html5DocType = new HtmlDocumentType();
echo $html5DocType;
// <!DOCTYPE html>
$html401StrictDocType = new HtmlDocumentType(
'-//W3C//DTD HTML 4.01//EN',
'http://www.w3.org/TR/html4/strict.dtd',
HtmlDocumentTypeInterface::PUBLIC_SYSTEM_KEYWORD_SYSTEM
);
echo html401StrictDocType;
// <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
If you already know the component parts of a doctype you might as well just create a string., (*5)
What is often more useful is taking an existing doctype string and parsing it into its component parts., (*6)
<?php
use webignition\HtmlDocumentType\HtmlDocumentTypeInterface;
use webignition\HtmlDocumentType\Parser\Parser;
use webignition\HtmlDocumentType\Parser\ParserInterface;
$parser = new Parser();
$html5DocTypeParts = $parser->parse('<!DOCTYPE html>');
var_dump($html5DocTypeParts);
// array(3) {
// 'public-system' => NULL
// 'fpi' => NULL
// 'uri' => NULL
// }
$html401StrictDocTypeParts = $parser->parse('<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">');
var_dump($html401StrictDocTypeParts);
// array(3) {
// 'public-system' => string(6) "PUBLIC"
// 'fpi' => string(25) "-//W3C//DTD HTML 4.01//EN"
// 'uri' => string(37) "http://www.w3.org/TR/html4/strict.dtd"
// }
Parsing a doctype string requires a doctype string. One of the most common places to find a doctype string is in a HTML document., (*7)
<?php
use webignition\HtmlDocumentType\Extractor;
$html5DocTypeString = Extractor::extract('<!DOCTYPE html><html>...</html>');
echo $html5DocTypeString;
// <!DOCTYPE html>
You can extract the doctype string from a HTML document, but what do you then do with it? One option is to create a HtmlDocumentType object., (*8)
use webignition\HtmlDocumentType\Factory;
// Create from a known doctype string
$html5DocumentType = Factory::createFromDocTypeString('<!DOCTYPE html>');
echo $html5DocType;
// <!DOCTYPE html>
// Create from a HTML document
$html5DocumentType = Factory::createFromHtmlDocument('<!DOCTYPE html><html>...</html>');
echo $html5DocType;
// <!DOCTYPE html>
Two of the component parts of a doctype are particularly relevant to validation: the fpi and the uri. There are known set of valid fpi values. For each valid fpi, there are a known set of valid uri values., (*9)
Need to check that your doctype's fpi is valid that the corresponding uri is valid for that fpi?, (*10)
use webignition\HtmlDocumentType\Factory;
use webignition\HtmlDocumentType\Validator;
$validator = new Validator();
$html5DocumentType = Factory::createFromDocTypeString('<!DOCTYPE html>');
$validator->isValid($html5DocumentType);
// true
$html401StrictDocumentType = Factory::createFromDocTypeString('<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">');
$validator->isValid($html401StrictDocumentType);
// true
$invalidDocumentType = new HtmlDocumentType('invalid FPI');
$validator->isValid($invalidDocumentType);
// false
// If the uri doesn't match what is expected for the fpi, the doctype is considered invalid
$laxHtml401StrictDocumentType = Factory::createFromDocTypeString('<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "foo">');
$validator->isValid($laxHtml401StrictDocumentType);
// false
// You can relax the strictness of validity. This is useful in cases where a doctype string uses the uri of a draft version of a HTML spec (the doctype string was once valid but is no longer)
$validator->setMode(Validator::MODE_IGNORE_FPI_URI_VALIDITY);
$validator->isValid($laxHtml401StrictDocumentType);
// true
// Relaxing validity strictness has no impact on invalid fpi values
$validator->setMode(Validator::MODE_IGNORE_FPI_URI_VALIDITY);
$validator->isValid($invalidDocumentType);
// false
You will need git to clone and composer to retrieve dependencies. I'm assuming both are in your path. Adjust as required., (*11)
git clone git@github.com:webignition/html-document-type.git
cd html-document-type
composer install
This project uses phpcs to check for PSR2 coding standards and phpunit for running the tests. Both are installed by composer as dev dependencies., (*12)
Composer scripts are present to run CS checks, to run tests or to run both., (*13)
# Coding standards checks
composer cs
> ./vendor/bin/phpcs src tests --colors --standard=PSR2
# Tests
composer test
> ./vendor/bin/phpunit --colors=always
PHPUnit 5.7.27 by Sebastian Bergmann and contributors.
................................ (and so on)
# Coding standards checks then tests
composer ci
> ./vendor/bin/phpcs src tests --colors --standard=PSR2
> ./vendor/bin/phpunit --colors=always
PHPUnit 5.7.27 by Sebastian Bergmann and contributors.
.................................... (and so on)
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