php session serializer

session.php

<?php

function sessionDataUnserialize($serializedData) {
    $return_data = array();
    $offset = 0;

    while ($offset < strlen($serializedData)) {
        if (!strstr(substr($serializedData, $offset), "|")) {
            throw new Exception("invalid data, remaining: " . substr($serializedData, $offset));
        }
        $pos = strpos($serializedData, "|", $offset);
        $num = $pos - $offset;
        $varname = substr($serializedData, $offset, $num);
        $offset += $num + 1;
        $data = unserialize(substr($serializedData, $offset));
        $return_data[$varname] = $data;
        $offset += strlen(serialize($data));
    }

    return $return_data;
}

function sessionDataSerialize(array $data) {
    $result = [];
    foreach ($data as $key => $value) {
        $result[] = $key . '|' . serialize($value);
    }

    return implode('', $result);
}

$sessionData = 'intkey|i:42;stringkey|s:3:"str";arraykey|a:2:{s:3:"int";i:42;s:6:"string";s:3:"str";}stdclasskey|O:8:"stdClass":2:{s:3:"int";i:42;s:6:"string";s:3:"str";}';

var_dump($sessionData === sessionDataSerialize(sessionDataUnserialize($sessionData)));