From the Raspberry Pi download page and shortened!
- Noobs - A way to try all the main ones in one re-imagiable download.
- Raspbian “wheezy” - Recommended, with development tools.
- Soft-float Debian “wheezy” - Same as Raspbian but compiled for the slower soft-float hardware. Used for Oracle JVM version 7 or less.
- Arch Linux ARM - Boots in 10 seconds but definitely not for beginners.
- Pidora - Fedora.
- RISC OS - Acorn.
One of the things that helped me out the most when I was learning Yii was their series on YouTube called Yii Developer’s Tutorial. I kind of stumbled across it when I was searching for help on getting started.
Unfortunately all the videos in the series didn’t seem to be listed anywhere. They were spread across 2 different peoples YouTube channels so it meant using the search engine to find the next episode!
I thought I’d group them together for you, like I did for the Armstrong & Miller - WWII RAF Sketches.
Introduction: Concepts, MVC architecture and Active Records.
Yii Architectural Review. Yii is scalable, supports CRUD actions, MVC but is not classed as an enterprise application framework because it doesn’t support transactions, no business rules or constraints, no workflow control.
There is a another set of vids (showing my age there!) can be found on Yii’s website in the screencasts section. These start with showing how a controller can write Hello World on the screen and go through the steps of getting Hello World from the database.
When learning Yii I found it difficult to match the different layout strategies used in the demo applications that are bundled with Yii, specifically Helloworld, Hangman and Blog.
A layout is essentially another view. Layouts are optional as everything can be done in the view. If all your pages share a common look or feel then you may want to refactor the majority of the static (or nearly static) content into the Layout, leaving the view to provide the body of the content that is specific to that page.
If you’ve written a lot of PHP applications then you’ll recognise the following:
If “The page and maybe some more PHP.” is the view then the rest is the layout. Or to put it another way a layout is a decorator for a view.
A nice example of this is the Blog demo. The view contains all the page specific body but the menus and side bars are held in the layout. You could add the layout to each view and not use layouts at all but this would mean repeating a lot of the same code across all the views.
The first thing to understand is the precedence of the layout overrides. As with all these things the closer to the code that’s running the higher the priority.
Action: With the highest priority, this layout can be set inside the body of the controller action.
public function actionIndex()
$this->layout = "mylayout";
Controller:The layout can be set at the controller level by overriding the layout variable from the base class.
- Theme: The layout may be taken from the current theme.
- Module: The layout may be taken from the current module.
- Parent Modules: If the current module has no layout, then traverse up its parents until you find one.
- Default: Finally the Yii application defines the default layout [
Yii::app()->layout] which is meant as a catch all.
- None: All these places are searched but if at the end of the day they don’t point to anything then a layout won’t be used.
This demo is the simplest because it does not render a view, it only outputs raw text (or data). Let’s trace the path through the application.
/helloworld/is accessed and Yii looks for the configuration file
/helloworld/protected/config/main.phpin order to find the first controller to load.
main.phpconfiguration file is not found so Yii then looks for the default controller called Site. It loads
- The default action for a controller is Index so
actionIndex()is called which just echos some stuff to the screen.
This demo uses a single layout for all pages.
/hangman/is accessed and Yii looks for the configuration file
/hangman/protected/config/main.phpin order to find the first controller to load.
- The defaultController is game, so Yii loads
- The default action has been set to “play” by overriding the
defaultActionfield of the
actionPlay()is called first.
- At the end of
render()is called with either “guess” as the view or “play". Let’s continue assuming “play” was selected.
- Now Yii will render
/protected/views/game/play.phpinto a variable.
- Next it will look for a layout to place that rendering. Following the priorities from above it will eventually get to the default layout for the application (CWebApplication) which is
- Yii will make sure that
layouts/main.phpexists then it will render that layout, setting $content to the result of rendering the view file.
This demo uses 3 layout files to render the site.
main.php is the default catch-all layout and
column2.php are intermediate layout files.
/blog/is accessed and Yii looks for the configuration file
/blog/protected/config/main.phpin order to find the first controller to load.
- The defaultController is post, so Yii loads
PostController.phpsets the class layout to “column2″, so all views will use “column2″ as their layout.
- The default action is Index so
actionIndex()is called next. When it gets to the end it calls
render()to render the index view.
/blog/protected/views/post/index.phpis used to draw the blog posts and the result is returned to the renderer.
- The renderer uses the result of the view-render as the $content in the column2 layout.
The column2 layout has the following form. It means that stuff between
endContentwill be given to
/layouts/mainas its $content.
There’s another pretty decent article on Larry Ullman’s site, Working with Layouts in Yii.
I would like to debug PHP in Eclipse PDT while it runs under an Apache server with a bit of MySQL thrown in. In order to do the remote debug one needs to configure PHP to use XDebug which is a standard cross-platform debugger that is used by a variety of languages to debug over the wire. It is based on DBGp, a common debugger protocol for languages and debugger UI communication.
I followed the standard instructions to switch on XDebug except that I installed it under
e:\xampp instead of the default
- Launch the XAMPP Control Panel.
- On the Apache row click Config, then PHP (php.ini) to load the PHP configuration file.
- Forward search for [XDebug]
Make sure the following options are uncommented (i.e. remove the semi-colon at the front of the line) and fill in the entries to match those below.
zend_extension = “E:\xampp\php\ext\php_xdebug.dll”
xdebug.remote_enable = 1
xdebug.remote_handler = “dbgp”
xdebug.remote_host = “127.0.0.1″
xdebug.remote_port = “9000″
- Stop Apache
- Start Apache
On starting Apache the following message pops up:
The procedure entry point zend_unmangled_property_name_ex could not be located in the dynamic link library php5ts.dll
After a lot of really boring reading in the usual forums and help web sites I find out that the
php_xdebug.dll is not compiled correctly for the version of PHP I’m using. This is very strange because it was downloaded as a bundle so everything should be compatible with everything else, but it wasn’t.
To confirm this type:
which gives the following output:
Failed loading E:\xampp\php\ext\php_xdebug.dll
Microsoft Windows dictates an internal DLL binary format which coincidentally is released with a new version of Microsoft’s Visual studio. This makes programs compiled with different versions of compiler incompatible with each other - thanks for that. It causes problems in every computer language that is compiled with a Microsoft compiler. PHP is just one of them. Python is another. If you compile Python under Visual Studio 9 you will have to recompile all the support modules with the same compiler. So not only do you have to care about whether it was compiled into 32 or 64 bit code but you also have to care about which compiler was used too.
The name of the XAMPP binary tells you which version of Visual ‘C’ was used to create the application suite. In my case I downloaded
xampp-win32-1.8.2-0-VC9-installer.exe. From the file name we can see that this is a windows 32 bit version compiled using Visual ‘C’ 9.
This only gives us some of the story. For the rest we need to run XAMPP and get it to tell us how it was compiled. In the document root
E:\xampp\htdocs create a file called p.php and fill it with:
<?php phpinfo(); ?>
Next open you browser and go to: http://127.0.0.1/p.php.
There are several lines of importance:
PHP Version 5.4.16
Compiler MSVC9 (Visual C++ 2008)
Zend Extension Build API220100525,TS,VC9
PHP Extension Build API20100525,TS,VC9
phpinfo() confirms that Microsoft’s Visual ‘C’ version 9 (MSVC9) was used as the compiler which was built in Visual C++ 2008. The Visual C++ 2008 tells us that the Apache needs the Visual C++ Redistribution libraries to be installed. You wouldn’t be able to run Apache with out them. If may explain why XAMPP may work on a newer server but give DLL errors on an older one.
x86 is the hardware architecture and indicates that it is a 32 bit build.
Zend Extension Build and PHP Extension Build have their compiler options although in this case the only important part of this is the TS bit. I think that in some builds of PHP the TS may not exist or it might be NTS instead.
Next we have to download a new version of XDebug that will fit into our environment. So navigate to:
In the Releases section look for the version that has the compiler flags we need. We’ll start with the latest version (XDebug 2.2.3 at the time of writing). I’m using PHP version 5.4 compiled using VC9 with TS and for a 32 bit build. So I download PHP 5.4 VC9 TS (32 bit) (php_xdebug-2.2.3-5.4-vc9.dll).
There are 2 ways to install it.
- Stop Apache
- Start Apache
Windows being what it is with locking files means that you have to stop Apache before copying the DLL in to the correct place which will slightly increase the downtime. This might work better as a tested upgrade on a production system where you don’t want to touch the configuration files.
Alternatively you can:
Edit the zend_extension line in the php.ini to point to this version.
zend_extension = “E:\xampp\php\ext\php_xdebug-2.2.3-5.4-vc9.dll”
xdebug.remote_enable = 1
- Stop Apache
- Start Apache
Most people choose this option because it gives you a better infrastructure for testing different versions as well as an easy rollback or upgrade path in case anything goes wrong. It also reminds you which version of XDebug you are using. The DLLs stay in place and you are only changing the configuration files. As a result there is no gap between the Apache restart.
Finally navigate to your
phpinfo() page and there should be a section for XDebug.
I spent almost half a day trying to figure out why the SD card plugged into the side of my MacBook Pro suddenly became read-only.
After wading through an awful lot of Apple forums containing “are you sure you have the SD card read-only lock in the correct position” I discovered several aspects of this problem that will hopefully save other people from pulling their hair out.
- The problem happens more often than not on SDHC type cards.
- Mac has some out-of-specification code to write to SD cards which is not compatible with other card readers.
- There is a fault with the onboard card reading which falsely reports that the physical read-only lock is active.
- It matters how you insert the SD card into the SD reader’s slot.
- All problems can be solved by using an external card reader.
The problem I was suffering from was that of the false positives on the SD card reader’s read-only sensor. The device file for the onboard SD card reader was
/dev/disk1 so I’ll use that in the work-around procedure that follows:
- Open a terminal window and type:
$ ls -l /dev/disk1*
br–r—– 1 mrn operator 14, 0 11 Jun 00:24 /dev/disk1
- Make sure the SD card’s physical switch is pressed down in the unlocked position. There should be a label on the card itself to remind you.
- Insert the card firmly applying the pressure directly along the line of insertion.
- Run the above line again to check the read-only status.
- If the device still reports as read-only, pull the card out and insert your fingernail in between the physical lock switch. The gap should remain when you remove your nail, then repeat the test.
- Increase the width by about a fingernail’s worth each time you run the test and eventually you will reach the sweet spot. The test will report:
$ ls -l /dev/disk1*
brw-rw—- 1 mrn operator 14, 0 11 Jun 00:24 /dev/disk1
It took me about 3 or 4 iterations to find the right point.