Social Issues – stoimen's web log

PHP Strings Don’t Need Quotes

Stoimen — Thu, 26 Apr 2012 13:52:53 +0000

I bet you didn’t know that PHP strings don’t need quotes! Indeed PHP developers work with strings with either single or double quotes, but actually in some cases you don’t need them.

PHP by Book

Here’s how PHP developer declare a string, which is something very common in any programming language.

$my_var = 'hello world';
// or
$my_var = "hello world";

PHP Tricks

What if you do the following:

echo hello;

That appears to be correct … Well, it’s not absolutely correct. You’ll be “noticed”.

// Notice: Use of undefined constant hello
echo hello;

However if you disable error reporting, the code will be completely fine.

error_reporting(0);

// no problem now
echo hello;

Variations

What follows from the thing above is that you can use strings without quotes:

// hello
echo hello;

// hello world (concatenated)
echo hello . ' world';

// helloworld
echo hello . world;

However you can’t have spaces and most of the “special” symbols.

// syntax error
echo hello world;

// syntax error
echo hello!;

Final Words

Although you can do this in PHP, that is completely wrong. The code becomes more difficult to read and understand. In the second place you can miss a $ sign in front of a variable declaration and thus the PHP interpreter will assume this is a string. So disable error reporting isn’t so great sometimes.

Download Files with Zend Framework

Stoimen — Tue, 25 May 2010 14:06:13 +0000

Download a File

The title may sound unclear enough, but the task is simple. You’ve to make a file download process within a Zend Framework’s controller. Let’s assume we’ve the DownloadController setup:


In PHP there are at least three simple lines of code that will do the job of downloading a file.
header('Content-Type: image/jpeg');
header('Content-Disposition: attachment; filename="logo.jpg"');
readfile('images/logo.jpg');

Note that here there is a content-type header, which is important cause the browsers understands what kind of file is supposed to be downloaded. The second line suggests a name of the downloaded file and the third one returns the file to the client.
Download a File ... within Zend Framework
Those three lines wont work alone in a ZF application, because there's no view, but even if you create a .phtml (view) file for this action it won't work, because the header of the returned file is modified.
The question is how to possibly return the file for download, perhaps write some statistics to the database and if there's a problem (some permission issues for instance) return a message to the user.
The Basic Solution
The solution is simple. First make it work by disabling the view and possibly the layout for this action:
public function indexAction()
{
	header('Content-Type: image/jpeg');
	header('Content-Disposition: attachment; filename="logo.jpg"');
	readfile('images/logo.jpg');
	
	// disable the view ... and perhaps the layout
	$this->view->layout()->disableLayout();
        $this->_helper->viewRenderer->setNoRender(true);
}

Than add some code where you can check the permissions. Just because there's no view for this action you can redirect to another - errorAction():
public function indexAction()
{
    if (userHasNoPermissions) {
        $this->view->msg = 'This file cannot be downloaded!';
        $this->_forward('error', 'download');
    }

    header('Content-Type: image/jpeg');
    header('Content-Disposition: attachment; filename="logo.jpg"');
    readfile('images/logo.jpg');

    // disable layout and view
    $this->view->layout()->disableLayout();
    $this->_helper->viewRenderer->setNoRender(true);
}

But that still will prompt you a file to download, so there should be a return statement that will return false:
public function indexAction()
{
    if (userHasNoPermissions) {
        $this->view->msg = 'This file cannot be downloaded!';
        $this->_forward('error', 'download');
        return FALSE;
    }

    header('Content-Type: image/jpeg');
    header('Content-Disposition: attachment; filename="logo.jpg"');
    readfile('images/logo.jpg');

    // disable layout and view
    $this->view->layout()->disableLayout();
    $this->_helper->viewRenderer->setNoRender(true);
}

So here's the complete source of DownloadController.php:
view->msg = 'This file cannot be downloaded!';
	        $this->_forward('error', 'download');
	        return FALSE;
	    }
	
	    header('Content-Type: image/jpeg');
	    header('Content-Disposition: attachment; filename="logo.jpg"');
	    readfile('images/logo.jpg');
	
	    // disable layout and view
	    $this->view->layout()->disableLayout();
	    $this->_helper->viewRenderer->setNoRender(true);
	}	
	
	public function errorAction()
	{}
}

and the error.phtml:
msg ?>


Related posts:

Setting Up Global Cache in Zend Framework 
Models in Zend Framework – Initialize All Methods with init() 
Upload a File with Zend Framework 
Download Images with PHP

How to detect a variable existence in JavaScript?

Stoimen — Fri, 12 Feb 2010 09:01:09 +0000

Preface

After reading one of the latest posts from Stoyan Stefanov’s blog – phpied.com I stumbled upon an interesting construction in JavaScript describing how to check an object property existence. I’m going to cover this case using as an example the console object, which comes with the Firebug enabled, and I think it may be very useful, just because this object is widely used, but doesn’t exists over all the browsers, even under Firefox when Firebug is disabled. This construction is known as the IN statement and it looks something like that:

property in object

which I’m going to cover later in details.

How you detect a variable existence?

There are three main ways to detect the existence of a property I see in my practice.

1. The most widely used:

if ( console ) { ... }

2. The second and more professional one:

if ( typeof console != 'undefined' ) { ... }

3. And finally the third and most unknown:

if ( console in window ) { ... }

Of course two of them are wrong! Which one should be changed?

Is everything working correctly? No!

Lets see how they are working. First of all I’m going to test all of them on Firefox 3.6 either with enabled and disabled Firebug, just shouting with old school’s alert().

Now the first one using the IN statement:

if ( console in window )
   alert('object exists!');
else
   alert('object doesn\'t exists!');

With Firebug disabled the answer is … nothing! No alert! That’s because the syntax is wrong. There’s an error within the IF statement. We should modify a bit the first row like that:

if ( 'console' in window )
   alert('object exists!');
else
   alert('object doesn\'t exists!');

Now everything’s OK. With a disabled Firebug the answer is: “object doesn’t exists!”, and after enabling it, normally the “object exists!”.

Lets move on the next example:

if ( console )
   alert('object exists!');
else
   alert('object doesn\'t exists!');

With Firebug enabled the answer is as we expect: “object exists!”, but after disabling it yet again – nothing?! Why’s that? Because the console object doesn’t exists anymore and the IF statement doesn’t return true or false, but simply crashes. How to modify the code? Simply by adding a window.console instead of console.

if ( window.console )
   alert('object exists!');
else
   alert('object doesn\'t exists!');

Than the answer is: “the object doesn’t exists!” after what we expected!

The third method is the mostly used, just because it’s completely clear what’s the goal of the IF statement:

if ( typeof console != 'undefined' )
   alert('object exists!');
else
   alert('object doesn\'t exists!');

In both disabled and enabled Firebug the answer is as expected!

Now the IN statement may be used if not for the console, but for checking the existence of a property of within an object.