PHP-and-MySQL/C2/Loops-While-Statement /English

From Script | Spoken-Tutorial
Revision as of 12:04, 29 November 2012 by Chandrika (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search
Time Narration
0:00 Hello and welcome. I have decided to create seperate tutorials for each looping statement.
0:07 I want to keep it simple. This will be useful as a reference also if you need to refer to how a particular loop works.
0:22 In this tutorial, we will learn about the WHILE loop
0:25 A WHILE loop checks for a condition at the start at the loop and executes the code depending on whether this condition is True or not
0:35 for example I'll start my 'WHILE loop' here and this is the condition and this is my block
0:44 I'll represent my block between curly brackets
0:52 My condition is here. Now, in the 'IF statement', for example I used 1=1.
1:02 Now if I say 'test' or 'loop' here.
1:08 There is a loop here and then a break. Now what happens is as long as 1=1, it would create a loop
1:14 If I do something here, lets try this.
1:19 It would probably crash your browser because the loop would be repeated as long as 1=1 and for infinite no. of times, 1 will always equal 1
1:29 So since the loop will always be repeated, your browser will crash
1:33 Lets say while a variable, 'num' is smaller or equal to 10 and under echo i can say - 'num ++'
1:57 '++' is an arithmetical operator. And what it basically does is, it increases num by 1. It is the same as writing 'num =num +1'
2:16 So it takes num and says that it is equal to the value of num plus 1.
2:22 So this again is an arithmetical operator. What's going to happen is -
2:29 We are going to say 'num' lesser than or equal to '10', if yes then echo loop and then say add 1 on to the variable num
2:46 But what we should really do is create 'num = 1' at the moment. So loop once at 1. This will then equal 2 then 3 then 4 all the way up to 10 and then it will stop
3:02 After that the rest of the code below this will continue
3:06 So we said this 1 and see what will we get. Okay we got a loop 1,2,3,4,5,6,7,8,10 times
3:20 Now to make it more fun I'll say loop 1 and I'll concatenate 'num' to the end of that
3:29 In fact let's make it simpler and say 'num' inside - it will make it easier to read
3:37 Okay I'll say loop 1 and add 1 and then I'll say loop 2 and I'll add another 1; that's loop 3 add another 1 up to 10.
3:49 Lets open this up. Refresh it. There you go. You got loop 1,2,3 all the way up to 10 as you can see
3:57 Lets change this value here to 100. Refresh that. You can see it has gone to hundred. The bigger the number, the longer it will take to loop
4:09 Let's take 6000. Let's refresh that. It's going to take a while. There you go - up to 6000. So it's very efficient in this way
4:20 You can try combining this with an 'array' to create a program that echoes out of the alphabet inside the 'array'
4:33 You can use loops to echo out every single value of an array
4:36 Just give it a go. I will probably do this in one my tutorial - not in the basics section though
4:45 However, this is the basics structure. What I also recommend you to do is create a variable here called 'max' and put your maximum value here
4:54 It will do exactly the same thing. It's just a lot more easy to read and you can declare all this here and this would be a reference to it
5:02 If you have more than 1 loop. I prefer it for readability and flexibility for my program. Okay so that's a WHILE loop. Let me summarise. It checks the condition of the start
5:15 If that condition is True. it would execute this block of code and you can do things like 'echo alpha'
5:21 Your variable is being incremented. Make sure that you do increment your variable otherwise it will loop for infinity.
5:31 Thanks for watching. This is Sidharth for the Spoken Tutorial Project, signing off. Goodbye.

Contributors and Content Editors

Chandrika