(EDIT: The question was clarified a bit since my first response)

I'm not aware of any research into handedness-based layouts. It sounds like an interesting idea and, as a lefty, I'd fall all over any app that catered to my inability to use my right hand like a normal person. However, I would caution that from a practical standpoint, you could probably not optimize for handedness in an automated fashion. To see why, let's suppose you used the accelerometer and were able to detect the hand being used 100% of the time. Perfect, except that you're measuring the wrong thing! The hand using the mobile device is not necessarily the dominant hand. Ever use your phone with your off-hand? Bam! Your app's interface is completely backwards, hindering rather than helping your user. In other words, handedness does not determine behavior.

So the best, most consistent way to do this would be to create a setting and send your lefties there. Maybe you could use the accelerometer for this purpose, for example, "it looks like you may be left-handed, would you like to switch to a left-handed layout?" I do not know the feasibility of using the accelerometer for this purpose, but it seems like it would not be trivial.

In my original response, I talked about the value of avoiding interactions with an obvious handedness, which I think still applies. (A) Your customers might not want to or know how to change settings (good defaults are important!) and (B) you'd make the job of customizing your UI that much easier. Take the iPhone's slide to unlock or slide to power down as an example.



As a lefty, this action was almost impossible for me to perform one-handed because it meant tucking my thumb in close to the left edge and pushing out. More than once, I have dropped my iPhone attempting to perform this action. This interaction clearly favors the right-handed. Now compare to the Windows Phone power down:



There's no clear handedness to this interaction. It works equally well for righties and lefties. I now use a Windows Phone.

It saddens me to say that if you absolutely must design an interaction with an obvious handedness, you should probably favor righties. They make up approximately 90% of the population.

Should you optimize mobile experiences based on individual handedness?
I just want to echo out some text on the webpage display with a tab space before a word.
I have the following codes in php:

&lt;?php
   echo "\t\t hello!&lt;br&gt;";
   echo "\t\t", "hello!&lt;br&gt;";
   echo "\t\t"."hello!&lt;br&gt;";
?&gt;


I tried all sorts of combinations, but it just won't show the tab spacing before the word.

OUTPUT:

hello!
hello!
hello!


I visited some links like: Newline escape sequence not working on php 
but I am not echoing it from a function. I just simply want to echo it out from a .php file.
