For efficiency, you're best to use a switch statement, and then to catch those you have not found in your cases, you can use a default.
switch(in_category){ //Begin switch statement.
case '7': //Check if it equals 7
include(TEMPLATEPATH . '/post-experts.php'); //Include our PHP code
break; //End this current condition.
case '6': //Check if it equals 6
include(TEMPLATEPATH . '/post-radio.php'); //Include our PHP code
break; //End this current condition.
case '5': //Check if it equals 5
include(TEMPLATEPATH . '/post-lifestyle.php'); //Include our PHP code
break; //End this current condition.
default: //If none of the above cases are found, do this.
include(TEMPLATEPATH . '/singleorigional.php'); //Include our PHP code
break; //End this current condition.
}
Edit: I decided to return to this at a later date, to better explain why this is better.
An if else combination implies an order. E.g.
if(thingy == "thing1"){
//Do one thing
}
elseif(thingy == "thing2"){
//Do another thing
}
elseif(thingy == "thing3"){
//Do a different thing
}
else{
//Catch anything
}
With this, it means it will check the first condition, if thing == thing1, if not, check if it equals the next condition which is thing == thing2 and so on. If you're generally always expecting thing1, then this might be okay, because you're just catching a few other things. However, realistically it's inefficient to check all possible conditions before you reach the solution you need.
Instead, by writing the equivalent switch statement:
switch(thingy){
case "thing1":
//Do one thing
break;
case "thing2":
//Do another thing
break;
case "thing3":
//Do a different thing
break;
default:
//Catch anything
break; //Break is not needed if default is the final case.
}
What this does instead, is grab the answer first, e.g. thing == "thing3", and then it'll skip the other cases that are irrelevant, and instead only do what it needs to do. It does not use an order, instead it works a bit like pointing to the correct answer. So it doesn't matter if your actual answer is the first case, or the hundredth, it only does what is relevant.
So to summarise: If you use a switch, and your answered case is the hundredth case, it'll point to what to do after that switch(answer) is found, if you were to use ifelse and your answer was the 100th variation of the ifelse, it would have to iterate through 99 other pointless checks before doing what it needs to do.