ogidimitrov/diff

Robust diff, match and patch for PHP, in the spirit of Google's Diff Match and Patch library.

• Diff — compute the character-based difference between two texts.
• Match — find the closest occurrence of a pattern in a text, tolerating typos.
• Patch — apply a list of edits to a text, best-effort, even if the text has drifted.

Highlights

• Pure PHP, no runtime dependencies beyond ext-mbstring.
• Fully UTF-8 aware: offsets, lengths and edits are measured in characters, so multi-byte text (accented letters, emoji, …) is never split in half.
• The familiar diff_main / match_main / patch_make API, plus the tuning properties (Diff_Timeout, Match_Threshold, Patch_Margin, …).
• Myers' diff algorithm with the usual speed-ups (common prefix/suffix trimming, a half-match heuristic and an automatic line-level pre-pass), the Bitap fuzzy matcher, and Unidiff-style patching.

Requirements

• PHP 8.1 or newer
• ext-mbstring

Installation

composer require ogidimitrov/diff

Usage

Diff

use OgiDimitrov\Diff\SimpleDiff;

$simpleDiff = new SimpleDiff();

$before = 'We meet in the morning to plan the week.';
$after  = 'We meet in the evening to plan the week ahead.';

$changes = $simpleDiff->diff_main($before, $after, false);

$changes is a list of [operation, text] pairs, where the operation is one of SimpleDiff::DIFF_EQUAL, SimpleDiff::DIFF_DELETE or SimpleDiff::DIFF_INSERT:

[
    [SimpleDiff::DIFF_EQUAL,  'We meet in the '],
    [SimpleDiff::DIFF_DELETE, 'mor'],
    [SimpleDiff::DIFF_INSERT, 'eve'],
    [SimpleDiff::DIFF_EQUAL,  'ning to plan the week'],
    [SimpleDiff::DIFF_INSERT, ' ahead'],
    [SimpleDiff::DIFF_EQUAL,  '.'],
]

A diff can be rendered as HTML, rehydrated into either text, or encoded compactly:

$simpleDiff->diff_prettyHtml($changes);         // HTML with <ins>/<del>
$simpleDiff->diff_text1($changes);              // $before
$simpleDiff->diff_text2($changes);              // $after
$simpleDiff->diff_levenshtein($changes);        // number of edits

$delta = $simpleDiff->diff_toDelta($changes);
$simpleDiff->diff_fromDelta($before, $delta);

Match

$text = 'It was the best of times, it was the worst of times.';

$simpleDiff->match_main($text, 'times', 0);    // 19 (nearest to the start)
$simpleDiff->match_main($text, 'times', 45);   // 46 (nearest to the end)
$simpleDiff->match_main($text, 'wrost');       // 37 (typo tolerated)
$simpleDiff->match_main($text, 'wersed');      // -1 (too far off)

$simpleDiff->Match_Threshold = 0.7;
$simpleDiff->match_main($text, 'wersed');      // 37

Patch

$before = 'We meet in the morning to plan the week.';
$after  = 'We meet in the evening to plan the week ahead.';

$patches = $simpleDiff->patch_make($before, $after);

echo $simpleDiff->patch_toText($patches);

@@ -12,11 +12,11 @@
 the
-mor
+eve
 ning
@@ -32,9 +32,15 @@
 the week
+ ahead
 .

Applying the patch to a text that has since drifted still works:

[$result, $applied] = $simpleDiff->patch_apply(
    $patches,
    'Every week we meet in the morning to plan the week.'
);

// $result  = 'Every week we meet in the evening to plan the week ahead.'
// $applied = [true, true]

The matcher locates each patch near where it was expected and reports, patch by patch, whether it landed. Placing a patch inside highly repetitive text is best-effort: the position chosen is implementation-defined and can differ slightly from other Diff Match and Patch ports.

Tuning

The original library's knobs are exposed as properties on the SimpleDiff instance:

Property	Default	Meaning
Diff_Timeout	1.0	Seconds to spend on a diff before giving up (0 = no limit).
Diff_EditCost	4	Cost of an empty edit when simplifying a diff.
Match_Threshold	0.5	Score at which a match is rejected (0.0 exact, 1.0 very loose).
Match_Distance	1000	Distance that scores a full 1.0 worse.
Match_MaxBits	int width	Bitap pattern length limit.
Patch_DeleteThreshold	0.5	Similarity required before a large deletion is accepted.
Patch_Margin	4	Context characters carried by each patch (minimum 1).

API

All methods live on OgiDimitrov\Diff\SimpleDiff.

Diff:

• diff_main(before, after, checklines = true)
• diff_cleanupMerge, diff_cleanupSemantic, diff_cleanupSemanticLossless, diff_cleanupEfficiency
• diff_commonPrefix, diff_commonSuffix
• diff_linesToChars, diff_charsToLines
• diff_levenshtein, diff_xIndex
• diff_toDelta, diff_fromDelta
• diff_text1, diff_text2, diff_prettyHtml

Match:

• match_main(text, pattern, loc = 0)

Patch:

• patch_make(a, b = null, c = null)
• patch_toText, patch_fromText
• patch_apply, patch_addPadding, patch_splitMax

Testing

composer install
composer test   # PHPUnit
composer stan   # PHPStan, level 9

The suite covers the documented behaviour, the awkward corners (empty inputs, multi-byte text, deadline expiry, malformed deltas, patches that cannot be placed, …) and a seeded randomised pass that checks the invariants every diff must satisfy: a diff rehydrates into both texts, its delta decodes back to the same diff, the clean-up passes never lose text, and patches serialise round-trip.

License

Released under the MIT License.

The algorithms are those of Google's Diff Match and Patch, originally written by Neil Fraser. This package is an independent implementation, not a copy of any existing port. See NOTICE for details.