provided by: 
Originally published at Internet.comHave you ever stopped to give directions to a lost driver from two states away? For the sake of providing an example, imagine your conversation went something like this:
"Hi, can you tell me how to get to route 50?"
"Sure, just follow this road, turn left onto the expressway, keep driving, and eventually you'll see the exit for route 50." The directions above were linear and sequential: drive on this road, turn here, and then drive until you see the exit. Obviously, they are horrible directions. They don't tell the driver how long to drive on the road before they reach the expressway or that they might want to take a different route to avoid traffic if they tried to leave during rush hour.
If you wanted to give more exact and useful directions, you might say something like:
"Sure, just follow this road for two miles. If its not rush hour, you can take a left at the lights onto the expressway and follow it for another mile until you see the exit for route 50. If you hit it near rush hour, you'll want to avoid the expressway and just follow the road for another 5 miles to route 50." Without Control Structures, PHP would be much like the first set of directions: linear, sequential, and not overly useful...
Read article at Internet.com site