This allows you to check for the existence of a variable (or check that the variable has a valid value) and assign a value accordingly. This is very useful when you are dealing with $_GET, $_POST, $_SESSION etc. variables, because you don't know whether the incoming variable will exist, and if it doesn't you might want to assign a default value.

An example is included and explained - evaluating an index in the _GET superglobal to see if it exists. It returns either the value itself or a false.

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.

His results found that the switch statement is generally more than 2 times as fast at matching a simple integer. His tests, however, didn't go through much more than this simple test. It'd be interesting to see what it would do with something more complex (like longer strings or handling the result of an evaluation inside the definition of the switch().