Difference between revisions of "PHP-and-MySQL/C2/Logical-Operators/English-timed"
From Script | Spoken-Tutorial
Sandhya.np14 (Talk | contribs) |
Sandhya.np14 (Talk | contribs) |
||
| Line 133: | Line 133: | ||
|- | |- | ||
|05:23 | |05:23 | ||
| − | |But for the 'OR' | + | |But for the 'OR' that doesn't really make sense and you can imagine what will happen. |
|- | |- | ||
|05:29 | |05:29 | ||
Revision as of 10:33, 20 May 2015
| 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 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 - 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. |
