Having learned OOP in Java, I am generally against multiple inheritance. I believe that if the answer is multiple inheritance, you’re asking the wrong question. But, for “academic” reasons, I tried to implement multiple inheritance in PHP. And I came up with the following abomination.

First, create a parent class from which all classes in need of multiple inheritance extend. The parent classes will be placed in the $_parents array as strings. When the main object is instantiated, the constructor creates objects from all the parent classes. And by using __call() I’m just going to redirect method calls on the main object to the first suitable parent object. I know it sounds complicated, so long story short, just read the code! I’m a developer, not a writer!

/**
 * Abomination class implementing multiple inheritance via
 * __call magic method
 */
abstract class MultipleInheritance
{
    /**
     * List of parent classes
     *
     * @var array
     * @access protected
     */
    protected $_parents = array();    

    /**
     * List of parent objects - generated automatically
     *
     * @var array
     * @access private
     */
    private $_parentObjects = array();

    /**
     * Constructor (thank you captain Obvious)
     *
     * - init the parent objects
     *
     * @access public
     */
    public function __construct()
    {
        foreach ($this->_parents as $parentClass) {
            $this->_parentObjects []= new $parentClass();
        }
    }

    /**
     * __call magic method
     *
     * @param string $name
     * @param array $arguments
     * @access public
     * @return mixed
     */
    public function __call($name, array $arguments)
    {
        foreach ($this->_parentObjects as $object) {
            if (method_exists($object, $name)) {
                return call_user_func_array(array($object, $name), $arguments);
            }
        }

        throw new Exception('No such method: ' . $name);
    }
}

Now, some very sexist implementations of Mom and Dad classes:

class Dad
{
    /**
     * Can parallel park
     *
     * @access public
     * @return void
     */
    public function park()
    {
        echo 'Look, I can parallel park' . PHP_EOL;
    }    

    /**
     * Can ground the kids
     *
     * @access public
     * @return void
     */
    public function ground()
    {
        echo 'Grounded by DAD' . PHP_EOL;
    }
}

class Mom
{
    protected $_parents = array('GrandMa');

    /**
     * Makes sandwiches
     *
     * @access public
     * @return void
     */
    public function makeSandwich()
    {
        echo 'Just making a sandwich' . PHP_EOL;
    }    

    /**
     * Can grounds the kids
     *
     * @access public
     * @return void
     */
    public function ground()
    {
        echo 'Grounded by MOM' . PHP_EOL;
    }
}

…and finally the child class:

class Child extends MultipleInheritance
{
    protected $_parents = array('Dad', 'Mom');
}

Let’s try it out:

$child = new Child();
$child->park();
$child->makeSandwich();
$child->ground();

And it works. And when two parent classes have the same method – ground() in this case – the method belonging to the first encountered class is executed. And voila, multiple inheritance in PHP. Well, sort of.

Now there’s a small problem with the instanceof operator. And by small problem I mean it doesn’t work and there’s no way to fix it. The following code

if ($child instanceof Mom) {
    echo get_class($child) . ' class inherits from Mom' . PHP_EOL;
} else {
    echo get_class($child) . ' class does not inherit from Mom' . PHP_EOL;
}

will always go on the “else” branch, although in my application’s logic, the Child class extends from the Mom class. And since PHP doesn’t allow overloading the operators, there’s no clean way to do this. Of course, there’s a hacky way around it, by adding an isInstanceOf() method to the MultipleInheritance class:

abstract class MultipleInheritance
{
    // ...

    /**
     * Check inheritance
     *
     * @param string $class
     * @access public
     * @return bool
     */
    public function isInstanceOf($class)
    {
        if (in_array($this->_parents, $class)) {
            return true;
        }

        foreach ($this->_parentObjects as $parent) {
            if ($parent instanceof MultipleInheritance) {
                if ($parent->isInstanceOf($class)) {
                    return true;
                }
            }
        }

        return false;
    }
}

…and using it to check inheritance:

if ($child->isInstanceOf('Mom')) {
    echo get_class($child) . ' class inherits from Mom' . PHP_EOL;
} else {
    echo get_class($child) . ' class does not inherit from Mom' . PHP_EOL;
}

But the abomination is not completed yet. Because I used method_exists() instead of is_callable(), magic methods in the parent class will not be detected. To fix this, just change the code from:

if (method_exists($object, $name)) {
    return call_user_func_array(array($object, $name), $arguments);
}

…to…

if (is_callable($object, $name)) {
    return call_user_func_array(array($object, $name), $arguments);
}

…and it will work. At last, the abomination is ready. Doctor Frankenstein would be proud! Here is a gist with the entire example: https://gist.github.com/1652646.

PS: DO NOT USE MULTIPLE INHERITANCE IN REAL LIFE APPLICATIONS!

The proper way to do it is by issuing a HTTP 307 – Temporary redirect header – which will instruct the browser to resend the data to the new URI, indicated by the Location field of the response.

header('HTTP/1.1 307 Temporary Redirect');
header('Location: new-location.php');

Just for the record, in pre-HTTP 1.1 browsers the POST data gets converted to GET, but if your users don’t use computers from the 90s, this won’t be a problem. And it works like a charm. In Chrome and Internet Explorer.

In Firefox and Opera, the browser will pop-up a dialog, informing the user that the data is being redirected to another page and asking the user’s permission to continue. Which is an extremely stupid standard behavior. Yes, it’s in the standard!

If the 307 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

…straight from the HTTP’s status codes bible, RFC 2616. Why do I say it’s a stupid specification? Because it is! It makes no sense to pop-up a dialog that might confuse the user when the data was already sent. For example, if I’m a malevolent webmaster, I already have the user’s data, so at this point displaying the dialog box is useless. I can save the data in my database and have a cronjob connect to the new page or do whatever I please with the POSTed information. However, if the redirect is legitimate, displaying the message box might confuse the user and have him cancel the request, which might break the application’s logic.

Great work guys, I’m moments away from converting the POST data into GET and send it in the URL…

$value = 'zero';

switch ($value) {
    case 0:
        echo 'value is zero';
        break;
    default:
        echo 'value is not zero';
        break;
}
echo PHP_EOL;

What do you think that the code above will print? Well…I’ll spare you the hassle and give you the answer:

% php test.php
value is zero

This weird behavior originates in the fact that PHP uses the equality operator (==) instead of the identity (===) one when evaluating expressions inside a switch statement. It’s basically the same as:

if ('foo' == 0) {
    echo 'bar';
}

…which also yields unexpected results. I hate this type of casting!!!

A problem arose when I wanted to import my existing emails from Evolution to Gmail. Although Google provides extensive documentation and even a migration API, I was unable to find something tailored for Evolution. After some Googling and asking around, I decided to use the – kind of lame, but nevertheless, effective – IMAP approach.
It’s quite simple:

• enable IMAP support in your Gmail CP
• add the newly created IMAP account to your Evolution
• in Evolution, copy all the emails from your regular account to your Gmail one
• wait for the IMAP account to synchronize with the server (it might take a while, depending on the number of emails/attachments)

All your current folders will be imported as labels in Gmail. For some unknown reason, it was unable to group all conversations, although I uploaded the “Sent” folder. Anyways, if you have a better idea, feel free to post a comment.

Basically is like this:

#!/usr/bin/env python

import datetime

start_date = datetime.date( year = 2010, month = 2, day = 1 )
end_date = datetime.date( year = 2010, month = 1, day = 1 )

list = []

if start_date <= end_date:
    for n in range( ( end_date - start_date ).days + 1 ):
        list.append( start_date + datetime.timedelta( n ) )
else:
    for n in range( ( start_date - end_date ).days + 1 ):
        list.append( start_date - datetime.timedelta( n ) )

for d in list:
    print d

This works, but is somewhat lame and not quite reusable. The most “python-ish” way to do it is to create a generator function that will yield the current date and can be used in a for loop. So I did it:

#!/usr/bin/env python
import datetime

def daterange( start_date, end_date ):
    if start_date <= end_date:
        for n in range( ( end_date - start_date ).days + 1 ):
            yield start_date + datetime.timedelta( n )
    else:
        for n in range( ( start_date - end_date ).days + 1 ):
            yield start_date - datetime.timedelta( n )

start = datetime.date( year = 2010, month = 2, day = 1 )
end = datetime.date( year = 2010, month = 1, day = 1 )

for date in daterange( start, end ):
    print date

Much more elegant

$originalArray = array(
    1 => 'First item',
    4 => 'Forth item',
    5 => 'Fift item',
    10 => 'Tenth item', // and so on
);

$insertAtBegining = array(
    0 => 'None',
);

$newArray = array_merge($insertAtBegining, $originalArray);

But it didn’t work. It was displaying something like:

Array
(
    [0] => None
    [1] => First item
    [2] => Forth item
    [3] => Fifth item
    [4] => Tenth item
)

Not a good result, because the arrays’ keys were actually primary keys used by the RDBMS so it was very important for me to keep the original keys. I didn’t want to take the lame approach and do a foreach loop:

$newArray = $insertAtBegining;
foreach($originalArray as $key => $value) {
    $newArray[$key] = $value;
}

…because it was too obvious, so I did something less obvious, and much more complicated:

$newArray = array_combine(
    array_merge(array_keys($insertAtBegining), array_keys($originalArray)),
    array_merge(array_values($insertAtBegining), array_values($originalArray))
);

But in the end, Chris, one of my colleagues who also has a blog at SegmentationFault.es pointed out the most simple and elegant solution:

$newArray = $insertAtBegining + $originalArray;

This reminds me of the saying “Keep It Simple Stupid” Which Chris uses as a wallpaper…

For instance, today the head of my company’s IT department showed me the following cool trick: if you have an XML file loaded in a buffer and you want to have it properly indented, you just hit Escape in your Vim editor and type

:% !xmllint --format %

… and…Magic!

Anyway, lately I’ve spent some time puting together a list of very useful plugins for PHP/Zend Framework and python/django development in order to speed things up and become more productive. My (g)Vim configuration currently uses:

• Vilight colorscheme by Rob Robbins
• snipMate by Michael Sanders
• NERD_Tree by Martin Grenfell
• django snippets by Rob Hudson
• AutoComplPop by Takeshi Nishida

And a custom gvimrc file. If you want to give it a try, check out my GitHub repository at http://github.com/motanelu/GVim-configuration. Installation is very simple, just follow the instructions below (PS: I’m using GVim. If you’re using Vim replace gvimrc with vimrc):

cd ~/
mv .vim .vim.bak
mv .gvimrc .gvimrc.bak
git clone git://github.com/motanelu/GVim-configuration.git
mv GVim-configuration .vim
ln -s ~/.vim/gvimrc ~/.gvimrc

Post a comment and tell me if you find it useful. If you’re a Zend Framework user, have a look over the snippets.

I went the easy way: right clicked on the clock in the upper right, selected “Adjust date and time” and made the modifications. After a few minutes the clock was showing Bucharest’s time and my changes were overwritten. I though I must have imagined setting the clock right in the first place – since I “tasted” Moritz thoroughly – and did it again.

I’ve ignored the clock for a while and, later on, when I looked at it, it was displaying Bucharest’s time again

D’oh! Ubuntu queries it’s time servers from time to time and sets the hour according to the information retrieved from these servers. And since my timezone was still set to Europe/Bucharest, on each update my system was receiving the time for that area. I’ve changed the timezone accordingly and everything started working. Magic!

To change the timezone of on you Ubuntu system go to System > Administration > Time and date. Or, if you’re a console freak, just punch in:

sudo dpkg-reconfigure tzdata

in order to set the correct time zone.

But, lately, I’ve used django for more ambitious projects and some obvious flaws began to annoy me. The first thing – the one this entry’s about – is the configuration file. Django comes with a settings.py file in which all the settings are being held, without any regard to their purpose.

Environment settings like database connection strings, file system paths and debuging are mixed together with application settings like what middleware classes are used, context processors and so on. So I’ve decided to split the configuration file in two, like in the following example:

local.py

This file holds the host related configuration and each instance of the application should have its own local.py file. One for development, one for testing, one for staging, one for production and so on. This file should not be included in the source control repository, so add a svn/git/whatever ignore on it.

# debug settings
DEBUG = True
TEMPLATE_DEBUG = DEBUG

# database configuration
DATABASE_ENGINE = ''
DATABASE_NAME = ''
DATABASE_USER = ''
DATABASE_PASSWORD = ''
DATABASE_HOST = ''
DATABASE_PORT = ''

# media root ex: /var/www/my-project/media
MEDIA_ROOT = ''

# media url ex: media.my-project.tld
MEDIA_URL = ''

# admin media url ex: /media
ADMIN_MEDIA_PREFIX = '/media/'

# application's secret key
SECRET_KEY = 'mY-S3Cr3t-K3y-m|_|st-b3-un1QuE-4nD-h4rD-t0-GueSs'

settings.py

This file holds the application related configurations and should be included in the version control system.

import os

# root directory for the project
ROOT_DIR = os.path.realpath( os.path.dirname( __file__ ) )

ADMINS = (
	( 'root', 'root@project.tld' ),
)

# import all the local settings
from local import *

MANAGERS = ADMINS
TIME_ZONE = 'Europe/Bucharest'

LANGUAGE_CODE = 'en-us'

SITE_ID = 1

USE_I18N = True

TEMPLATE_LOADERS = (
    'django.template.loaders.filesystem.load_template_source',
    'django.template.loaders.app_directories.load_template_source',
)

MIDDLEWARE_CLASSES = (
    'django.middleware.cache.UpdateCacheMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.middleware.cache.FetchFromCacheMiddleware',
)

ROOT_URLCONF = 'my-project.urls'

TEMPLATE_CONTEXT_PROCESSORS = (
    'django.core.context_processors.auth',
    'django.core.context_processors.debug',
    'django.core.context_processors.i18n',
    'django.core.context_processors.media',
)

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
)

# template directories
TEMPLATE_DIRS = (
    os.path.join( ROOT_DIR, 'templates' ),
    os.path.join( ROOT_DIR, 'other', 'template', 'path' ),
)

# django debug toolbar configuration
INTERNAL_IPS = ( '127.0.0.1' )
if DEBUG:
    MIDDLEWARE_CLASSES += 'debug_toolbar.middleware.DebugToolbarMiddleware',
    INSTALLED_APPS += 'debug_toolbar',

The last bit is because I usually use in development the incredibly useful Django debug_toolbar, and of course, I want it turned off on the live environment.

echo preg_match('/^\\([a-z]+)/', $word) ? 'match' : 'no match';

…but it won’t work. Furthermore, it will yield an error saying something like:

Compilation failed: unmatched parentheses at offset …

And it makes sense, since the backslash has a special meaning, as it’s the escape character, to give it a literal meaning you have to escape it. Like such:

echo preg_match('/^\\\\([a-z]+)/', $word) ? 'match' : 'no match';

…each of the two backslashes is escaped by another backslash placed in front of it. But this also doesn’t work The correct way to do it is:

echo preg_match('/^\\\\\\\\([a-z]+)/', $word) ? 'match' : 'no match';

Yeap. That’s right! With 8 backslashes. For each backslash you wanted matched, you need to add 4 in the regular expression. That’s because the backslash is considered to be an escape character by both PHP’s parser and its regexp engine. So, if you type a backslash in PHP, it’s considered and escape character by PHP’s parser.

If you write two backslashes in PHP, this construct will be interpreted as a literal backslash by PHP’s paser and sent to the regexp engine as an escape character. That’s right: ‘\\’ in PHP means a ‘\’ for the regexp engine. So, in order to pass a literal backslash to the regexp engine, you need to add 4 backslashes in PHP.

This is what I call backslash hell