php-merge

Introduction

When working with revisions of text one sometimes faces the problem that there are several revisions based off the same original text. Rather than choosing one and discarding the other we want to merge the two revisions.

Git does that already wonderfully. In a php application we want a simple tool that does the same. There is the xdiff PECL extension which has the xdiff_string_merge3 function. But xdiff_string_merge3 does not behave the same way as git and xdiff may not be available on your system.

PhpMerge is a small library that solves this problem. There are two classes: \PhpMerge\PhpMerge and \PhpMerge\GitMerge that implement the \PhpMerge\PhpMergeInterface which has just a merge method.

PhpMerge uses SebastianBergmann\Diff\Differ to get the differences between the different versions and calculates the merged text from it. GitMerge uses Symplify\GitWrapper\GitWrapper, writes the text to a temporary file and uses the command line git to merge the text.

Usage

Simple example:

use PhpMerge\PhpMerge;

// Create a merger instance.
$merger = new PhpMerge();

// Get the texts to merge.
$original = <<<'EOD'
unchanged
replaced
unchanged
normal
unchanged
unchanged
removed

EOD;

$version1= <<<'EOD'
added
unchanged
replacement
unchanged
normal
unchanged
unchanged

EOD;

$version2 = <<<'EOD'
unchanged
replaced
unchanged
normal??
unchanged
unchanged

EOD;

$expected = <<<'EOD'
added
unchanged
replacement
unchanged
normal??
unchanged
unchanged

EOD;

$result = $merger->merge($original, $version1, $version2);
// $result === $expected;

With merge conflicts:

// Continuing from before with:
use Phpmerge\MergeException;
use PhpMerge\MergeConflict;


$conflicting = <<<'EOD'
unchanged
replaced
unchanged
normal!!
unchanged
unchanged

EOD;

try {
    $merger->merge($original, $version2, $conflicting);
} catch (MergeException $exception) {
    /** @var MergeConflict[] $conflicts */
    $conflicts = $exception->getConflicts();

    $original_lines = $conflicts[0]->getBase();
    // $original_lines === ["normal\n"];
    
    $version2_lines = $conflicts[0]->getRemote();
    // $version2_lines === ["normal??\n"];
    
    $conflicting_lines = $conflicts[0]->getLocal();
    // $conflicting_lines === ["normal!!\n"];
    
    $line_numer_of_conflict = $conflicts[0]->getBaseLine();
    // $line_numer_of_conflict === 3; // Count starts with 0.
    
    // It is also possible to get the merged version using the first version
    // to resolve conflicts.
    $merged = $exception->getMerged();
    // $merged === $version2;
    // In this case, but in general there could be non-conflicting changes.
    
    $line_in_merged = $conflicts[0]->getMergedLine();
    // $line_in_merged === 3; // Count starts with 0.
}

Using the command line git to perform the merge:

use PhpMerge\GitMerge;

$merger = new GitMerge();

// Use as the previous example.

Installation

PhpMerge can be installed with Composer by adding the library as a dependency to your composer.json file.

{
    "require": {
        "bircher/php-merge": "~4.0"
    }
}

To use the command line git with GitMerge:

{
    "require": {
        "bircher/php-merge": "~4.0",
        "symplify/git-wrapper": "^9.1|^10.0"
    }
}

Please refer to Composer's documentation for installation and usage instructions.

Difference to ~3.0

In the ~4.0 version we switch from cpliakas/git-wrapper to symplify/git-wrapper since the former is deprecated. This update means that there is no change when only using PhpMerge\PhpMerge.