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 OR 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 vertical 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 is "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 - let's 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 make 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