Ping Pong

I'm going to show you some other loops that I prefer 0:00 when it comes to looping through arrays. 0:03 But I don't want you to think that while loops are unimportant. 0:05 Let's create a simple ping pong game to demonstrate another use case for 0:08 while loops. 0:14 Let's create a new file named pingpong.php We add our PHP tags. 0:15 And then we're ready to start programming the game. 0:27 We'll start with two players, each with an initial score of 0. 0:30 $player1 = 0. 0:36 And $player2 = 0. 0:38 I also want to track how many rounds each game takes. 0:42 So I'm going to add another variable. 0:45 $round = 0. 0:47 Now let's add some comments. 0:52 To win, a player must reach the score of 11. 0:55 While also being a minimum of 2 points higher than their opponent. 0:58 So while those conditions are not met. 1:02 I'm going to randomly increment one of the player's scores each round. 1:05 To check for the difference between the player scores, 1:10 I can subtract one score from the other. 1:13 This will give me a number that can be positive or 1:16 negative depending on which score is higher. 1:18 We can then find the absolute value of that number. 1:22 Let me demonstrate. 1:26 Let's change $player2 = 5. 1:28 Then we'll do a var_dump. 1:32 $player1- $player2. 1:37 Then we'll also var dump $player2- $player1. 1:41 Let's run the script. 1:51 I see that the first var dump shows -5 and this the second var dump shows 5. 1:55 The difference between these numbers is 5. 2:02 All I care about is that the difference between these numbers is greater than 2. 2:06 I don't care which is the higher number. 2:10 So, I can use a function to determine the absolute value, abs. 2:13 I'll add this to the first var_dump. 2:21 Now, when I run my script. 2:25 You can see that the absolute value gives me the number itself, 2:28 without the negation before it. 2:33 I can use this absolute value in my while loop. 2:36 Let’s comment out these var dumps. 2:39 So I want to continue to loop while the absolute value is less than 2. 2:48 I also want to continue to loop while both scores are less than 11. 2:58 So I'm going to add a second expression. 3:04 I’ll combine these with the double pipe 3:06 operator because I want either or to be true. 3:11 $player1 is less than 11 and 3:17 $player2 is less than 11. 3:22 I need to put parenthesis around these two expressions so 3:26 that they evaluate as a single conditional. 3:29 $player1 must be less than 11 and 3:34 $player2 must be less than 11 to continue my loop. 3:37 So if the difference between the players is less than 2, we'll continue to loop. 3:43 Or if $player1 and $player2 are both less than 11 we will continue to loop. 3:48 The first thing I want to do is to start incrementing the round. 3:56 This would be round 1. 4:00 So adding 1 to 0 = 1. 4:02 Let's also let the user know what's going on with each loop. 4:07 So let's start with the heading for the round. 4:11 I want to view this in the browser, so let's add the HTML tags. 4:14 Round $round, And close my tags. 4:20 Notice that I used the double quote, so that my variable is expanded. 4:29 Now we want to randomly add a point to either $player1 or $player2. 4:34 PHP has a function named RAND that will generate a random integer. 4:40 We can specify a minimum and a maximum for this random integer. 4:46 So we can say if {rand(0,1) 4:51 then we're going to do something. 4:56 The min and max are inclusive, meaning it will include the minimum and 5:02 the maximum in its random number generation. 5:08 With a minimum of 0 and a maximum of 1, 5:11 we will randomly receive either 0 or 1. 5:14 Since 0 evaluates to false and 1 evaluates to true, 5:19 we can use this in our conditional. 5:24 If 1 is returned and our expression is true, we can add 1 to $player1. 5:27 Else we can add 1 to $player2. 5:35 Now, let's display the current score for this round. 5:42 Player1 = $player1 score and a line break 5:47 Player2 = $player2 score and a line break. 5:58 And that's all we need for a while loop. 6:05 So let's preview this script in a browser. 6:07 We can see each round with a point being awarded to a random player. 6:12 And the final score ending with Player1 = 2 and Player2 having 11. 6:17 This is okay, but let's add a final summary. 6:25 After our while loop, we should add our comment back up in the while loop. 6:29 And after our comment we can add echo header 1. 6:40 If $player1 > $player2, 6:48 we'll echo Player1. 6:56 Else we'll echo Player2. 7:02 And finally we'll echo, 7:10 is the winner after $round rounds. 7:14 And close our header. 7:20 Let's preview our script again to see the final result. 7:24 Player 2 is the winner after 9 rounds. 7:29