Difference between revisions of "PHP-and-MySQL/C2/Logical-Operators/English-timed"
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− | |What is a '''logical operator'''? Let's add a bit of logic and say it's the ' | + | |What is a '''logical operator'''? Let's add a bit of logic and say it's the '''AND''' or the '''OR''' operator. |
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|00:27 | |00:27 | ||
− | |Now if I start creating my basic layout for my | + | |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. |
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|00:43 | |00:43 | ||
− | |Before we had example such as '1 is greater than 1' which at the moment is going to return ' | + | |Before we had example such as '1 is greater than 1' which at the moment is going to return '''False''' |
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|00:54 | |00:54 | ||
− | | | + | |Let's just check it to see where we are.... right!. So that's "False". |
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|01:04 | |01:04 | ||
− | |Now what if I said "if 1 is greater than 1 or equals 1". | + | |Now, what if I said "if 1 is greater than 1 or equals 1". |
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|01:18 | |01:18 | ||
− | |Now we don't write it as ' | + | |Now we don't write it as 'OR', we write it as two vertical lines or two pipes. |
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|01:26 | |01:26 | ||
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|01:38 | |01:38 | ||
− | |So if we compile this, what do you think the result is gonna be? | + | |So, if we compile this, what do you think the result is gonna be? |
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|01:43 | |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... | + | |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... |
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|01:54 | |01:54 | ||
− | |We know that 1 equals to 1 is "true" | + | |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". |
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|02:09 | |02:09 | ||
− | | | + | | '''OR''', either of these could be "true" to make this. |
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|02:12 | |02:12 | ||
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|02:16 | |02:16 | ||
− | |Okay, so that's the 'OR'. | + | |Okay, so that's the '''OR'''. |
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|02:18 | |02:18 | ||
− | |Basically it allows you to take two comparisons, show them in your '''if''' statement and if either of them | + | |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... |
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|02:30 | |02:30 | ||
− | | | + | |either of them are "true", you will be left with "true". |
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|02:34 | |02:34 | ||
− | |'''AND''' | + | |''''AND' operator''' is a different manner. |
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|02:39 | |02:39 | ||
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|02:46 | |02:46 | ||
− | |So we have got "false" here because 1 is not greater than 1. | + | |So, we have got "false" here because 1 is not greater than 1. |
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|02:51 | |02:51 | ||
− | |We'll go back to our comparison operators and we will say "if 1 is greater than 1 or equal to 1 ''' | + | |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". |
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|03:04 | |03:04 | ||
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|03:10 | |03:10 | ||
− | |But I am pretty sure that you have got the hang of variables by now | + | |But I am pretty sure that you have got the hang of variables by now by following my other tutorials. |
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|03:17 | |03:17 | ||
− | |So these are the two '''logical operators'''. | + | |So, these are the two '''logical operators'''. |
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|03:20 | |03:20 | ||
− | |You will find them very useful because you might want to say for example | + | |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. |
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|03:30 | |03:30 | ||
− | |It is a "login" form. Say, a user wants to 'login' into a website. | + | |It is a "login" '''form'''. Say, a user wants to 'login' into a website. |
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|03:35 | |03:35 | ||
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|03:52 | |03:52 | ||
− | |So we can say, for example: | + | |So, we can say, for example: |
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|03:54 | |03:54 | ||
− | |If the username, in fact let's do this, I'll say | + | |If the username, in fact let's do this, I'll say '$username' is equal to "alex" and my '$password' is equal to "abc". |
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|04:04 | |04:04 | ||
− | |Now I will substitute these. I can say "username" | + | |Now, I will substitute these. I can say "username" '''AND''' (&&) "password". |
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|04:11 | |04:11 | ||
− | |At the moment, this will say " | + | |At the moment, this will say "True". |
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|04:15 | |04:15 | ||
− | |I'll change this. I'll say | + | |I'll change this. I'll say "OK" or "you forgot to fill out a field" because there will eventually be '''HTML fields'''. |
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|04:27 | |04:27 | ||
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|04:32 | |04:32 | ||
− | |So let's try it. Yes, that's saying " | + | |So, let's try it. Yes, that's saying "OK". |
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|04:37 | |04:37 | ||
− | |Now what happens if I forget to type my password in there? There's nothing in there at the moment - no space - | + | |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. |
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|04:48 | |04:48 | ||
− | | | + | |"You forgot to fill out a field". |
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|04:50 | |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. | + | |So, if you imagine these are coming from the user - so it has been submitted as you typed your "username" and "password" in. |
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|05:00 | |05:00 | ||
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|05:23 | |05:23 | ||
− | |But for the ' | + | |But for the 'OR' that doesn't really make sense and you can imagine what will happen. |
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|05:29 | |05:29 | ||
− | |So right now, this will equal "true" because we have got both values. So this is | + | |So right now, this will equal "true" because we have got both values. So this is "OK". |
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|05:36 | |05:36 | ||
− | |Now if I go with both of them and try it out. | + | |Now, if I go with both of them and try it out. |
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|05:41 | |05:41 | ||
− | | | + | |If the username exists, so the username is "True"... |
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|05:45 | |05:45 | ||
− | |At the moment there is no value - so it is " | + | |At the moment there is no value - so it is "False". |
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|05:48 | |05:48 | ||
− | | | + | |or the password is true - that is the value exists, at the moment it doesn't, so it is "False". |
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|05:56 | |05:56 | ||
− | |So we are going to say "You forgot to fill out a field". | + | |So, we are going to say "You forgot to fill out a field". |
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|06:00 | |06:00 | ||
− | |I'll just write here | + | |I'll just write here "Nothing" because at the moment it means nothing. |
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|06:05 | |06:05 | ||
− | |So '''refresh'''. I'll make it | + | |So '''refresh'''. I'll make it "Nothing". |
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|06:08 | |06:08 |
Latest revision as of 21:02, 19 December 2018
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. |