(PECL xdiff >= 0.2.0)
xdiff_string_patch — Patch a string with an unified diff
$str
   , string $patch
   [, int $flags
   [, string &$error
  ]] )
   Patches a str string with an unified patch in patch parameter 
   and returns the result. patch has to be an unified diff created by 
   xdiff_file_diff()/xdiff_string_diff() function. 
   An optional flags parameter specifies mode of operation. Any
   rejected parts of the patch will be stored inside error variable if 
   it is provided.
  
strThe original string.
patchThe unified patch string. It has to be created using xdiff_string_diff(), xdiff_file_diff() functions or compatible tools.
flags
       flags can be either
       XDIFF_PATCH_NORMAL (default mode, normal patch)
       or XDIFF_PATCH_REVERSE (reversed patch).
      
       Starting from version 1.5.0, you can also use binary OR to enable
       XDIFF_PATCH_IGNORESPACE flag.
      
errorIf provided then rejected parts are stored inside this variable.
   Returns the patched string, or FALSE on error.
  
Example #1 xdiff_string_patch() example
The following code applies changes to some article.
<?php
$old_article = file_get_contents('./old_article.txt');
$diff = $_SERVER['patch']; /* Let's say that someone pasted a patch to html form */
$errors = '';
$new_article = xdiff_string_patch($old_article, $diff, XDIFF_PATCH_NORMAL, $errors);
if (is_string($new_article)) {
    echo "New article:\n";
    echo $new_article;
}
if (strlen($errors)) {
    echo "Rejects: \n";
    echo $errors;
}
?>