PHP中如何比较两个文本文件的差异，类似于版本管理

PHP中如何比较两个文本文件的差异，类似于版本管理

下面是个diff.php，检测两段代码差异性

<?php

/*

class.Diff.php

A class containing a diff implementation

Created by Stephen Morley - http://stephenmorley.org/ - and released under the
terms of the CC0 1.0 Universal legal code:

http://creativecommons.org/publicdomain/zero/1.0/legalcode

*/

// A class containing functions for computing diffs and formatting the output.
class Diff{

  // define the constants
  const UNMODIFIED = 0;
  const DELETED    = 1;
  const INSERTED   = 2;

  /* Returns the diff for two strings. The return value is an array, each of
   * whose values is an array containing two values: a line (or character, if
   * $compareCharacters is true), and one of the constants DIFF::UNMODIFIED (the
   * line or character is in both strings), DIFF::DELETED (the line or character
   * is only in the first string), and DIFF::INSERTED (the line or character is
   * only in the second string). The parameters are:
   *
   * $string1           - the first string
   * $string2           - the second string
   * $compareCharacters - true to compare characters, and false to compare
   *                      lines; this optional parameter defaults to false
   */
  public static function compare(
      $string1, $string2, $compareCharacters = false){

    // initialise the sequences and comparison start and end positions
    $start = 0;
    if ($compareCharacters){
      $sequence1 = $string1;
      $sequence2 = $string2;
      $end1 = strlen($string1) - 1;
      $end2 = strlen($string2) - 1;
    }else{
      $sequence1 = preg_split('/\R/', $string1);
      $sequence2 = preg_split('/\R/', $string2);
      $end1 = count($sequence1) - 1;
      $end2 = count($sequence2) - 1;
    }

    // skip any common prefix
    while ($start <= $end1 && $start <= $end2
        && $sequence1[$start] == $sequence2[$start]){
      $start ++;
    }

    // skip any common suffix
    while ($end1 >= $start && $end2 >= $start
        && $sequence1[$end1] == $sequence2[$end2]){
      $end1 --;
      $end2 --;
    }

    // compute the table of longest common subsequence lengths
    $table = self::computeTable($sequence1, $sequence2, $start, $end1, $end2);

    // generate the partial diff
    $partialDiff =
        self::generatePartialDiff($table, $sequence1, $sequence2, $start);

    // generate the full diff
    $diff = array();
    for ($index = 0; $index < $start; $index ++){
      $diff[] = array($sequence1[$index], self::UNMODIFIED);
    }
    while (count($partialDiff) > 0) $diff[] = array_pop($partialDiff);
    for ($index = $end1 + 1;
        $index < ($compareCharacters ? strlen($sequence1) : count($sequence1));
        $index ++){
      $diff[] = array($sequence1[$index], self::UNMODIFIED);
    }

    // return the diff
    return $diff;

  }

  /* Returns the diff for two files. The parameters are:
   *
   * $file1             - the path to the first file
   * $file2             - the path to the second file
   * $compareCharacters - true to compare characters, and false to compare
   *                      lines; this optional parameter defaults to false
   */
  public static function compareFiles(
      $file1, $file2, $compareCharacters = false){

    // return the diff of the files
    return self::compare(
        file_get_contents($file1),
        file_get_contents($file2),
        $compareCharacters);

  }

  /* Returns the table of longest common subsequence lengths for the specified
   * sequences. The parameters are:
   *
   * $sequence1 - the first sequence
   * $sequence2 - the second sequence
   * $start     - the starting index
   * $end1      - the ending index for the first sequence
   * $end2      - the ending index for the second sequence
   */
  private static function computeTable(
      $sequence1, $sequence2, $start, $end1, $end2){

    // determine the lengths to be compared
    $length1 = $end1 - $start + ...

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