optimizing a switch statement

iamaphpfreak

Say I have a switch statement that runs through cases numbered 1-100:

What is the most optimal way to run this switch?

switch($a){

case 1:

case 2:

...
}

NogDog

I don't see any way to give a useful answer to this without knowing what exactly you want to accomplish functionally with such a switch construct. (For all I know, using a switch might not even be the best pattern for whatever it is you are trying to do.)

iamaphpfreak

It's basically a person has 100 options to choose from in a dropdown menu.

For each option he chooses, he gets a different output.

The drop-down is a form, so I use GET to retrieve the variable.

Then, I would use a switch on the variable.
case 1: case 2:, case 3:....

Would it be better to use a nested switch?

case 1:
case 1-25:
case 2:
case 26-50:
case 3:
case 51-75:
case 4:
case 76-100:

Would this improve runtime?

NogDog

Is each of the 100 cases unique in what it does? If not, then you can group the duplicates together:

switch($var)
{
  case 1:
  case 5:
  case 73:
  case 99:
    echo "something";
    break;
  case 44:
  case 52:
  case 88:
    echo "something else";
    break;
  <etc....>
}

If certain cases are more likely to occur than others, then the more likely cases should probably be near the top of the list.

As an alternative, you could consider populating an array:

$outputs = array(
  1 => "output number one",
  "output number two",
  "output number three",
  "etc., etc., and so forth"
);
if(array_key_exists($var, $outputs))
{
  echo $outputs[$var];
}
else
{
  echo "default message or error message here";
}

iamaphpfreak

so, a nested switch statement would not enhance the speed?

Weedpacket

Is it too slow now? If you can't answer that then you're not yet in a position to know what if anything would "enhance the speed".

NogDog

I'm not 100% sure what you mean by a "nested switch statement". If it does save you anything, you're likely talking a few milliseconds at best. (At worst, it actually makes it slower.) Unless you are coding for a very high volume application or a realtime system like a missile guidance system, you're probably better served going for the easiest to read and thus easiest to maintain solution.

For that matter, when I see something with 100 or more options, the first thing I'm thinking is to let the database do the work instead of typing all that stuff into my code.

iamaphpfreak

thanks, sounds good. It takes about a second to run it, but I'm trying to reduce the runtime as much as I can.

Weedpacket

If it's taking that long it's not the switch statement slowing things down. Try and find out what actually needs optimising before trying to optimise.