Rob Thompson

Often, with little rhyme or reason behind it, I choose between using a switch condition or an if-else statement while coding simple condition matches in PHP. I got curious about which is actually more efficient at matching a random integer with a set of conditionals. So, I setup a script to create a set of large scripts to test the speed of these different constructs. Using the ‘time’ command, I measured the speed at which the condition could match a random number. Here is what I found:

  The switch construct is generally more than twice as fast at matching a simple integer within a single large set of conditions.

There is largely little difference between the time it takes to find a condition using if,if statements or if-elseif statements. Also the size of the resulting scripts were only negligibly different compared to the difference in execution time.

At first I thought that since the switch statement breaks execution after it matches its value especially since I was using random numbers, that this could account for the time difference, but that also had no bearing. Setting $var=999999 in the below statements had little effect on the faster execution time of the switch statement.

If-Elseif

<?
$var=rand(0,1000000);
if ($var==0)
  {
  echo "found 0";
  }
elseif ($var==1)
  {
  echo "found 1";
  }
elseif ($var==2)
  {
  echo "found 2";
  }
 
....
?>

If,If

<?
$var=rand(0,1000000);
if ($var==1)
  {
  echo "found 1";
  }
if ($var==2)
  {
  echo "found 2";
  }
if ($var==3)
  {
  echo "found 3";
  }
....
?>

Switch

<?
$var=rand(0,1000000);
switch ($var)
  {
   case 1: 
      echo "found 1";
      break;
   case 2: 
      echo "found 2";
      break;
   case 3: 
      echo "found 3";
      break;
....
?>

Also, I wondered if the switch condition would overall be less efficient if there were a large number of switch statements within a script, instead of a single switch construct with many cases. The thinking was that the switch condition was possibly more expensive to setup than an if-else. However, in this case, many switch statements still performed faster (around 25% more) than when using many if-else or if,if conditionals instead. This was tested with 100,000 iterations of 10 conditions as opposed to a 1 iteration of 1,000,000 conditions.

Of course, the if else construct is a bit more powerful for more complex condition testing, but if you only have a simple variable to match up against a known set of values, I guess the winner is the switch condition!