Функция PHP xdiff_file_diff
bool xdiff_file_diff ( string file1, string file2, string dest [, int context [, bool minimal]] )
xdiff_file_diff makes unified diff of files file1 and file2 and stores result in file dest. context indicated how many lines of context you want to include in diff result. Set minimal to TRUE if you want to minimalize size of diff (can take a long time). Resulting file is human-readable.
Замечание: This function doesn't work well with binary files. To make diff of binary files use xdiff_file_diff_binary.
Возвращает TRUE в случае успешного завершения или FALSE в случае возникновения ошибки.
xdiff_file_diff example The following code makes unified diff of two php files.
$old_version = 'my_script.php';
$new_version = 'my_new_script.php';
xdiff_file_diff($old_version, $new_version, 'my_script.diff', 2);
See also xdiff_string_diff.