check serialized data

gistfile1.txt

<?php
// Add yer string!
$data = '';

define('PATTERN', '/s:(\d+):"(.*?)";([Obis]):((\d+):)?([^;]+);/');

// Care not for arrays.
$blob = preg_replace('/a:\d+:{/', "\n", $data);

// Can't cope with objects.
$blob = preg_replace('/":\d+:{/', "\";\n", $blob);

Tidy up cleaned array and object closing braces.
$blob = preg_replace('/}/', "\n", $blob);

$blob = trim($blob);
$blob = implode('', explode("\n", $blob));

function variable_type($type) {
  switch($type) {
  case 'O':
    return 'Object';
  case 'a':
    return 'Array';
  case 'b':
    return 'Boolean';
  case 'i':
    return 'Integer';
  case 's':
    return 'String';
  }
  return 'Unknown ('. $type .')';
}

$errors = array();

$count = preg_match_all(PATTERN, $blob, $matches, PREG_SET_ORDER);


foreach ($matches as $match) {
  $type = variable_type($match[3]);

  // Key name is in $matches[2] and its length is in $matches[1].
  if (strlen($match[2]) != $match[1]) {
    $errors[] = sprintf ("%s variable name `%s' has incorrectly serialized name. Length is %d but should be %d.", $type, $match[2], $match[1], strlen($match[2]));
  }

  // Value $matches[6] and length in $matches[5].
  switch ($match[3]) {
  case 'O':
    $errors[] = sprintf("I know nothing about objects, but I will check variables inside `%s() %s'.", trim($match[6], '"'), $match[2]);
    break;
  case 'a':
    $errors[] = sprintf("I know nothing about arrays. Whatever `%s' might be ...", $match[2]);
    break;
  case 'b':
    if ($match[6] < 0 || $match[6] > 1) {
      $errors[] = sprintf("%s variable `%s' contains junk data: %s.", $type, $match[2], $match[6]);
    }
    break;
  case 'i':
    if (!is_numeric($match[6])) {
      $errors[] = sprintf("%s variable `%s' contains junk data: `%s'.", $type, $match[2], trim($match[6]));
    }
    break;
  case 's':
    $text = trim($match[6], '"');
    if (strlen($text) != $match[5]) {
      $errors[] = sprintf ("%s variable `%s' has incorrectly serialized value `%s'. Length is %d but should be %d.", $type, $match[2], $text, $match[5], strlen($text));
    }
    break;
  default:
    $errors[] = sprintf("Junk for %s variable `%s'.", $type, $match[2]);
    break;
  }
}

if (!empty($errors)) {
  printf("I detected %d problems:\n%s\n", count($errors), implode("\n", $errors));
  return count($errors);
} else {
  printf("Well, that all looks fine to me, though I did not check for array sizes.\n");
  return 0;
}