Best way for fast processing

As a PHP programmer faced a lot with (deepgoing) statements I'm curious how you handle this. Are you using switch, if-elseif-else or 开发者_StackOverflowif-else structures?

I personally prefer using the switch selector when dealing with more than 2 cases. Is this also the best way from a performance perspective? And how about nested statements?

I'm curious to your preferred methods and answers.

Example

The need of three-option-selector:

Using switch:

switch($option)
{
  case 1 : $result= "foo"; break;
  case 2 : $result= "bar"; break;
  default : $result= "foobar";
}

Using if-elseif-else

if($option == 1)
{
  $result= "foo";
} elseif ($option == 2)
{
  $result= "bar";
} else
{
  $result= "foobar";
}

Using if-if-else

if($option == 1)
{ 
  $handle = "foo";
}
if($option == 2)
{
  $result = "bar";
}
else
{
  $result = "foobar";
}

---

Everyone but the novice programmer knows that a switch is faster than an if..else, but a switch can't replace every compound expression you might put in an if statement (such as two expressions with a logical AND)

Also, if you're talking about deeply nested code like this

function foo()
{
  if ( /* expr1 */ )
  {
    // code

    if ( /* expr2 */ )
    {
      // code 

      if (  /* expr3 */ )
      {
        // code
        if ( /* expr4 */ )
        {
          // code          
        }
      }
    }
  } 
}

Then all I can say is, please stop doing that. Have some guard conditions that will force the function to exit early instead. Here's the above re-written with this style.

function foo()
{
  if ( !/* exp r1 */ )
  {
    return;
  }
  // code 1

  if ( !/* expr 2 */ )
  {
    return;
  }
  // code 2

  if ( !/* expr 3 */ )
  {
    return;
  }
  // code 3

  if ( !/* expr 4 */ )
  {
    return;
  }
  // code 4
}

Of course, both of these in a real application could probably be refactored even better by adding more functions.

---

I find switch handy when you have one piece of logic shared amongst many cases. ie.

case 1:
case 2:
case 3:
    // do stuff for 1, 2 and 3
    break;
case 4:
    // other stuff just for 4
    break;
default:
    // fallback for everything else
    break;

its also important to note that switch does loose comparison which might be undesired in certain scenarios

don't have too much to say from a performance point of view

---

I usually prefer to use the neatest looking, most understandable method. However, I try and avoid ever needing to ask the question. Having to use a large amount of if/else blocks in your code indicates a problem with your design.
Given that it is easy to create associative arrays, there is no reason why you can't map a key to a function or value which will probably outperform switch statements for anything other than trivial data sets. Or even better use polymorphism which is a far neater solution and often turns a large if or switch block into a single function call.

---

I would say if you look at the three examples, the most beautiful and clean one is easy to pick: The switch statement. If you can live with switch's loose comparison, pick that. On that level, performance considerations are usually pointless as the potential gains are minuscule.

---

If you need these kind of micro-optimizations, you should use another language. As a lazy programmer, I like to go for this kind of things :

class blabla{
  private $_actions;
  public function __construct(){
    $this->_actions = array(1 => '_firstAction',
                            2 => '_secondAction',
                            3 => '_thirdAction');

  }
  public function whatever($choice){
    if(isset($this->_actions[$choice])){
      $this->{$this->_actions[$choice]}();
    }
  }
  private function _firstAction(){}
  private function _secondAction(){}
  private function _thirdAction(){}
}