phpserialize 1.3

a port of the serialize and unserialize functions of php to python.

a port of the serialize and unserialize functions of php to python. This module implements the python serialization interface (eg: provides dumps, loads and similar functions).

Usage

>>> from phpserialize import *
>>> obj = dumps("Hello World")
>>> loads(obj)
'Hello World'

Due to the fact that PHP doesn’t know the concept of lists, lists are serialized like hash-maps in PHP. As a matter of fact the reverse value of a serialized list is a dict:

>>> loads(dumps(range(2)))
{0: 0, 1: 1}

If you want to have a list again, you can use the dict_to_list helper function:

>>> dict_to_list(loads(dumps(range(2))))
[0, 1]

It’s also possible to convert into a tuple by using the dict_to_tuple function:

>>> dict_to_tuple(loads(dumps((1, 2, 3))))
(1, 2, 3)

Another problem are unicode strings. By default unicode strings are encoded to ‘utf-8’ but not decoded on unserialize. The reason for this is that phpserialize can’t guess if you have binary or text data in the strings:

>>> loads(dumps(u'Hello W\xf6rld'))
'Hello W\xc3\xb6rld'

If you know that you have only text data of a known charset in the result you can decode strings by setting decode_strings to True when calling loads:

>>> loads(dumps(u'Hello W\xf6rld'), decode_strings=True)
u'Hello W\xf6rld'

Dictionary keys are limited to strings and integers. None is converted into an empty string and floats and booleans into integers for PHP compatibility:

>>> loads(dumps({None: 14, 42.23: 'foo', True: [1, 2, 3]}))
{'': 14, 1: {0: 1, 1: 2, 2: 3}, 42: 'foo'}

It also provides functions to read from file-like objects:

>>> from StringIO import StringIO
>>> stream = StringIO('a:2:{i:0;i:1;i:1;i:2;}')
>>> dict_to_list(load(stream))
[1, 2]

And to write to those:

>>> stream = StringIO()
>>> dump([1, 2], stream)
>>> stream.getvalue()
'a:2:{i:0;i:1;i:1;i:2;}'

Like pickle chaining of objects is supported:

>>> stream = StringIO()
>>> dump([1, 2], stream)
>>> dump("foo", stream)
>>> stream.seek(0)
>>> load(stream)
{0: 1, 1: 2}
>>> load(stream)
'foo'

This feature however is not supported in PHP. PHP will only unserialize the first object.

Array Serialization

Starting with 1.2 you can provide an array hook to the unserialization functions that are invoked with a list of pairs to return a real array object. By default dict is used as array object which however means that the information about the order is lost for associative arrays.

For example you can pass the ordered dictionary to the unserilization functions:

>>> from collections import OrderedDict
>>> loads('a:2:{s:3:"foo";i:1;s:3:"bar";i:2;}',
...       array_hook=OrderedDict)
collections.OrderedDict([('foo', 1), ('bar', 2)])

Object Serialization

PHP supports serialization of objects. Starting with 1.2 of phpserialize it is possible to both serialize and unserialize objects. Because class names in PHP and Python usually do not map, there is a separate object_hook parameter that is responsible for creating these classes.

For a simple test example the phpserialize.phpobject class can be used:

>>> data = 'O:7:"WP_User":1:{s:8:"username";s:5:"admin";}'
>>> user = loads(data, object_hook=phpobject)
>>> user.username
'admin'
>>> user.__name__
'WP_User'

An object hook is a function that takes the name of the class and a dict with the instance data as arguments. The instance data keys are in PHP format which usually is not what you want. To convert it into Python identifiers you can use the convert_member_dict function. For more information about that, have a look at the next section. Here an example for a simple object hook:

>>> class User(object):
...     def __init__(self, username):
...         self.username = username
...
>>> def object_hook(name, d):
...     cls = {'WP_User': User}[name]
...     return cls(**d)
...
>>> user = loads(data, object_hook=object_hook)
>>> user.username
'admin'

To serialize objects you can use the object_hook of the dump functions and return instances of phpobject:

>>> def object_hook(obj):
...     if isinstance(obj, User):
...         return phpobject('WP_User', {'username': obj.username})
...     raise LookupError('unknown object')
...
>>> dumps(user, object_hook=object_hook)
'O:7:"WP_User":1:{s:8:"username";s:5:"admin";}'

PHP’s Object System

The PHP object system is derived from compiled languages such as Java and C#. Attributes can be protected from external access by setting them to protected or private. This does not only serve the purpose to encapsulate internals but also to avoid name clashes.

In PHP each class in the inheritance chain can have a private variable with the same name, without causing clashes. (This is similar to the Python __var name mangling system).

This PHP class:

class WP_UserBase {
    protected $username;

    public function __construct($username) {
        $this->username = $username;
    }
}

class WP_User extends WP_UserBase {
    private $password;
    public $flag;

    public function __construct($username, $password) {
        parent::__construct($username);
        $this->password = $password;
        $this->flag = 0;
    }
}

Is serialized with a member data dict that looks like this:

>>> data = {
...     ' * username':          'the username',
...     ' WP_User password':    'the password',
...     'flag':                 'the flag'
... }

Because this access system does not exist in Python, the convert_member_dict can convert this dict:

>>> d = convert_member_dict(data)
>>> d['username']
'the username'
>>> d['password']
'the password'

The phpobject class does this conversion on the fly. What is serialized is the special __php_vars__ dict of the class:

>>> user = phpobject('WP_User', data)
>>> user.username
'the username'
>>> user.username = 'admin'
>>> user.__php_vars__[' * username']
'admin'

As you can see, reassigning attributes on a php object will try to change a private or protected attribute with the same name. Setting an unknown one will create a new public attribute:

>>> user.is_admin = True
>>> user.__php_vars__['is_admin']
True

To convert the phpobject into a dict, you can use the _asdict method:

>>> d = user._asdict()
>>> d['username']
'admin'

Python 3 Notes

Because the unicode support in Python 3 no longer transparently handles bytes and unicode objects we had to change the way the decoding works. On Python 3 you most likely want to always decode strings. Because this would totally fail on binary data phpserialize uses the “surrogateescape” method to not fail on invalid data. See the documentation in Python 3 for more information.

Changelog

1.3

• added support for Python 3

1.2

• added support for object serialization

• added support for array hooks

1.1

• added dict_to_list and dict_to_tuple

• added support for unicode

• allowed chaining of objects like pickle does