PHP-and-MySQL/C2/Logical-Operators/English-timed

Time	Narration
00:00	Hello and welcome to a tutorial on Logical Operators. It's a very brief tutorial but I will keep it like that at the moment.
00:09	I'll use an example of an "if" statement again because that's all I have got at the moment.
00:18	What is a logical operator? Let's add a bit of logic and say it's the 'and' or the horizontal line operator.
00:27	Now if I start creating my basic layout for my "if" statement, I will get to work on showing you what you can do with these.
00:43	Before we had example such as '1 is greater than 1' which at the moment is going to return 'false'
00:54	let's just check it to see where we are.... right . So that's "false".
01:04	Now what if I said "if 1 is greater than 1 or equals 1".
01:18	Now we don't write it as 'or' we write it as two horizontal lines or two pipes.
01:26	Not quite sure about that but if you know my keyboard it will be next to the shift key - two vertical lines that means 'OR'.
01:38	So if we compile this, what do you think the result is gonna be?
01:43	Now let's run through this once - if 1 is greater than 1 - "false" and so we have written "false" or 1 is equal to 1...
01:54	We know that 1 equals to 1 is "true"; so here we are saying 'or' 1 is equal to 1 not 'and' because if we said 'and' then both would have to be "true".
02:09	or either of these could be "true" to make this.
02:12	The output. So hopefully we get "true".
02:16	Okay so that's the 'OR'.
02:18	Basically it allows you to take two comparisons, show them in your "if" statement and if either of them are "true" - then it's like an "either" operator...
02:30	"either" of them are "true", you will be left with "true".
02:34	"AND" operator is a different manner.
02:39	"and" requires both of these to be "true" for this to be executed.
02:46	So we have got "false" here because 1 is not greater than 1.
02:51	We'll go back to our comparison operators and we will say "if 1 is greater than 1 or equal to 1 'and' 1 equal 1", here we will get "true".
03:04	So now, all I can really think is about to add a few variables in to this test.
03:10	But I am pretty sure that you have got the hang of variables by now, by following my other tutorials.
03:17	So these are the two logical operators.
03:20	You will find them very useful because you might want to say for example - this is a very classic example. You'll find it in one of my projects....
03:30	It is a "login" form. Say a user wants to login into a website.
03:35	You've probably logged into a website before and it said to enter your "username" and "password". Now the keywords are in here.
03:43	We need to check if the users have entered the "username" and the "password".
03:48	If they haven't, there is no point in comparing the "username" to the "password".
03:52	So we can say, for example.
03:54	If the username in fact let's do this. I'll say "username" is equal to "alex" and my password is equal to "abc".
04:04	Now I will substitute these. I can say "username" and "password".
04:11	At the moment, this will say "true".
04:15	I'll change this. I'll say 'ok' or 'you forgot to fill out a field' because there will eventually be HTML fields.
04:27	This is going to be okay because we have got both values.
04:32	So let's try it. Yes, that's saying "ok".
04:37	Now what happens if I forget to type my password in there? There's nothing in there at the moment - no space - lets get rid of that.
04:48	'You forgot to fill out a field'.
04:50	So if you imagine these are coming from the user - so it has been submitted as you typed your "username" and "password" in.
05:00	We are saying "username" and "password"; basically "username" itself is "true" because it exists...
05:07	If you had that inside, that would be acceptable; that would be "true".
05:14	We'll just check that there you go.
05:18	So because we have got "username" and "password" then that's fine.
05:23	But for the 'or' that doesn't really makes sense and you can imagine what will happen.
05:29	So right now, this will equal "true" because we have got both values. So this is 'ok'.
05:36	Now if I go with both of them and try it out.
05:41	"if the username exists" so the username is "true"...
05:45	At the moment there is no value - so it is "false".
05:48	"or the password is true" - that is, the value exists; at the moment it doesn't, so it is "false".
05:56	So we are going to say "You forgot to fill out a field".
06:00	I'll just write here nothing because at the moment it means nothing.
06:05	So refresh I'll make it nothing.
06:08	So you see, already I have explained how useful these can be in so many every day php applications.
06:17	For example - a form someone can fill in. You will find many other users for it.
06:22	But that's it then.
06:24	Two operators that are logical operators.
06:27	Just try them out and see what all you can do with them.
06:31	I will be using these most definitely in one of my projects quite soon.
06:35	Thanks for watching.
06:37	This is Sidharth dubbing for the Spoken Tutorial project.

Contributors and Content Editors

Gaurav, Minal, Pratik kamble, Sandhya.np14