How to unserialize D7 session? This is how the user session is stored in Drupal 7:

batches|a:46:{i:13;b:1;i:14;b:1;i:15;b:1;i:16;b:1;i:17;b:1;i:18;b:1;i:19;b:1;i:20;b:1;i:21;b:1;i:22;b:1;i:23;b:1;i:24;b:1;i:25;b:1;i:26;b:1;i:27;b:1;i:28;b:1;i:29;b:1;i:30;b:1;i:31;b:1;i:32;b:1;i:33;b:1;i:34;b:1;i:35;b:1;i:36;b:1;i:37;b:1;i:38;b:1;i:39;b:1;i:40;b:1;i:41;b:1;i:42;b:1;i:43;b:1;i:44;b:1;i:45;b:1;i:46;b:1;i:47;b:1;i:48;b:1;i:49;b:1;i:50;b:1;i:51;b:1;i:52;b:1;i:53;b:1;i:54;b:1;i:55;b:1;i:56;b:1;i:57;b:1;i:58;b:1;}updates_remaining|a:0:{}dblog_overview_filter|a:2:{s:4:"type";a:0:{}s:8:"severity";a:1:{i:2;s:1:"2";}}


How do I convert it to a PHP array? unserialize() does not work.
That's a session encoded string (different from a PHP serialized string). There's no built-in way to decode it directly into a variable, so you'll have to use a custom function.

Here's one nicked from the docs page for session_decode().

function unserializesession( $data ) {
  if(strlen( $data) == 0) {
    return array();
  }

  // match all the session keys and offsets
  preg_match_all('/(^|;|\})([a-zA-Z0-9_]+)\|/i', $data, $matchesarray, PREG_OFFSET_CAPTURE);

  $returnArray = array();

  $lastOffset = null;
  $currentKey = '';
  foreach ( $matchesarray[2] as $value ) {
    $offset = $value[1];
    if(!is_null( $lastOffset)) {
      $valueText = substr($data, $lastOffset, $offset - $lastOffset );
      $returnArray[$currentKey] = unserialize($valueText);
    }
    $currentKey = $value[0];

    $lastOffset = $offset + strlen( $currentKey )+1;
  }

  $valueText = substr($data, $lastOffset );
  $returnArray[$currentKey] = unserialize($valueText);

  return $returnArray;
}


It works well with the example in your question, returning a nested array of values.