How can I restructure `if` and `else` statements in PHP

I have two (and sometimes) three variables which determine if I should run a specific code. The problem is that any of them can be true or false and sometimes this leads to messy codes.

For three variables, there are 8 possible scenarios that I have to check. Like this:

if($var_a && $var_b && $var_c) {
   // Do this (A)
} else if(!$var_a && $var_b && $var_c) {
   // Do this (B)
} else if($var_a && !$var_b && $var_c) {
   // Do this (C)
} else if(!$var_a && !$var_b && $var_C) {
  // Do this (D)
}
... and so on.

Is there any way to use nesting and make this code less messy? It gets confusing at times to keep track of so many possibilities.

It might be easier to understand what I am saying with an example of two variables.

if($var_a && $var_b) {
  // Do this (A)
} else if($var_a && !$var_b) {
  // Do this (B)
} else if(!$var_a && $var_b) {
  // Do this (C)
}

Is there any way to combine these conditions together so that I don't have to use so many && and if else conditions? This will make things less confusing for me when I have to deal with three (may be more) variables.