A library for comparing two HTML files/snippets and highlighting the differences using simple HTML.

v0.1.11 2021-02-02 11:07 UTC


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php-htmldiff is a library for comparing two HTML files/snippets and highlighting the differences using simple HTML.

This HTML Diff implementation was forked from rashid2538/php-htmldiff and has been modified with new features, bug fixes, and enhancements to the original code.

For more information on these modifications, read the differences from rashid2538/php-htmldiff or view the CHANGELOG.


The recommended way to install php-htmldiff is through Composer. Require the caxy/php-htmldiff package by running following command:

composer require caxy/php-htmldiff

This will resolve the latest stable version.

Otherwise, install the library and setup the autoloader yourself.

Working with Symfony

If you are using Symfony, you can use the caxy/HtmlDiffBundle to make life easy!


use Caxy\HtmlDiff\HtmlDiff;

$htmlDiff = new HtmlDiff($oldHtml, $newHtml);
$content = $htmlDiff->build();


The configuration for HtmlDiff is contained in the Caxy\HtmlDiff\HtmlDiffConfig class.

There are two ways to set the configuration:

  1. Configure an Existing HtmlDiff Object
  2. Create and Use a HtmlDiffConfig Object

Configure an Existing HtmlDiff Object

When a new HtmlDiff object is created, it creates a HtmlDiffConfig object with the default configuration. You can change the configuration using setters on the object:

use Caxy\HtmlDiff\HtmlDiff;

// ...

$htmlDiff = new HtmlDiff($oldHtml, $newHtml);

// Set some of the configuration options.

// Calculate the differences using the configuration and get the html diff.
$content = $htmlDiff->build();

// ...

Create and Use a HtmlDiffConfig Object

You can also set the configuration by creating an instance of Caxy\HtmlDiff\HtmlDiffConfig and using it when creating a new HtmlDiff object using HtmlDiff::create.

This is useful when creating more than one instance of HtmlDiff:

use Caxy\HtmlDiff\HtmlDiff;
use Caxy\HtmlDiff\HtmlDiffConfig;

// ...

$config = new HtmlDiffConfig();

// Create an HtmlDiff object with the custom configuration.
$firstHtmlDiff = HtmlDiff::create($oldHtml, $newHtml, $config);
$firstContent = $firstHtmlDiff->build();

$secondHtmlDiff = HtmlDiff::create($oldHtml2, $newHtml2, $config);

$secondContent = $secondHtmlDiff->build();

// ...

Full Configuration with Defaults:

$config = new HtmlDiffConfig();
    // Percentage required for list items to be considered a match.
    // Set the encoding of the text to be diffed.
    // If true, a space will be added between the <del> and <ins> tags of text that was replaced.
    // Option to disable the new Table Diffing feature and treat tables as regular text.
    // Pass an instance of \Doctrine\Common\Cache\Cache to cache the calculated diffs.

    // Disable the HTML purifier (only do this if you known what you're doing)
    // This bundle heavily relies on the purified input from ezyang/htmlpurifier
    // Set the cache directory that HTMLPurifier should use.
    // Group consecutive deletions and insertions instead of showing a deletion and insertion for each word individually. 
    // List of characters to consider part of a single word when in the middle of text.
    ->setSpecialCaseChars(array('.', ',', '(', ')', '\''))
    // List of tags to treat as special case tags.
    ->setSpecialCaseTags(array('strong', 'b', 'i', 'big', 'small', 'u', 'sub', 'sup', 'strike', 's', 'p'))
    // List of tags (and their replacement strings) to be diffed in isolation.
        'ol'     => '[[REPLACE_ORDERED_LIST]]',
        'ul'     => '[[REPLACE_UNORDERED_LIST]]',
        'sub'    => '[[REPLACE_SUB_SCRIPT]]',
        'sup'    => '[[REPLACE_SUPER_SCRIPT]]',
        'dl'     => '[[REPLACE_DEFINITION_LIST]]',
        'table'  => '[[REPLACE_TABLE]]',
        'strong' => '[[REPLACE_STRONG]]',
        'b'      => '[[REPLACE_B]]',
        'em'     => '[[REPLACE_EM]]',
        'i'      => '[[REPLACE_I]]',
        'a'      => '[[REPLACE_A]]',
    // Sets whether newline characters are kept or removed when `$htmlDiff->build()` is called.
    // For example, if your content includes <pre> tags, you might want to set this to true.



Contributor Code of Conduct

Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms. See CODE_OF_CONDUCT file.


Did we miss anyone? If we did, let us know or put in a pull request!


php-htmldiff is available under GNU General Public License, version 2. See the LICENSE file for details.


  • Tests, tests, and more tests! (mostly unit tests) - need more tests before we can major refactoring / cleanup for a v1 release
  • Add documentation for setting up a cache provider (doctrine cache)
    • Maybe add abstraction layer for cache + adapter for doctrine cache
  • Make HTML Purifier an optional dependency - possibly use abstraction layer for purifiers so alternatives could be used (or none at all for performance)
  • Expose configuration for HTML Purifier (used in table diffing) - currently only cache dir is configurable through HtmlDiffConfig object
  • Performance improvements (we have 1 benchmark test, we should probably get more)
    • Algorithm improvements - trimming alike text at start and ends, store nested diff results in memory to re-use (like we do w/ caching)
    • Benchmark using DOMDocument vs. alternatives vs. string parsing
    • Consider not using string parsing for HtmlDiff in order to avoid having to create many DOMDocument instances in ListDiff and TableDiff
  • Benchmarking
  • Refactoring (but... tests first)
    • Overall design/architecture improvements
    • API improvements so a new HtmlDiff isn't required for each new diff (especially so that configuration can be re-used)
  • Split demo application to separate repository
  • Add documentation on alternative htmldiff engines and perhaps some comparisons