Pravin1389: moved PHP-and-MySQL/C2/Logical-Operators /English to PHP-and-MySQL/C2/Logical-Operators/English

2012-12-01T13:09:03Z

moved PHP-and-MySQL/C2/Logical-Operators /English to PHP-and-MySQL/C2/Logical-Operators/English

Chandrika: Created page with '{| border=1 !Time !Narration |- |0:0 |Hello and welcome to a tutorial on "Logical Operators". Its a very brief tutorial but I will keep it like that at the moment. |- |0:09 |I'l…'

2012-11-29T06:32:38Z

Created page with '{| border=1 !Time !Narration |- |0:0 |Hello and welcome to a tutorial on "Logical Operators". Its a very brief tutorial but I will keep it like that at the moment. |- |0:09 |I'l…'

New page

{| border=1
!Time
!Narration
|-
|0:0
|Hello and welcome to a tutorial on "Logical Operators". Its a very brief tutorial but I will keep it like that at the moment.
|-
|0:09
|I'll use an example of an "if" statement again because that's all I have got at the moment.
|-
|0:18
|What is a logical operator? Let's add a bit of logic and say its the 'and' or the 'or' operator.
|-
|0:27
|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.
|-
|0:43
|Before we had example such as 1 is greater than 1 which at the moment is going to return 'false'
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|0:54
|let's just check it to see where we are.... right . So that's "false".
|-
|1:02
|Now what if I said "if 1 is greater than 1 or 1 equals 1".
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|1:18
|Now we don't write it as 'or' we write it as two horizontal lines or two pipes.
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|1:27
|Not quiet sure about that but if know my keyboard it would next to the shift key - two horizontal lines and that means 'or'.
|-
|1:38
|So if we compile this what do you think the result is gonna be?
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|1:43
|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...
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|1:54
|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".
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|2:04
|or either of these could be "true" to make this.
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|2:07
|The output. So hopefully we will get "true".
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|2:14
|Okay so that's the 'or'.
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|2:17
|It basically allows you to take two comparisons, show them into your "if" statement and if either of them are "true" - so its like an "either" operator...
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|2:29
|"either" of them are "true", you will be left with "true".
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|2:35
|"and" operator is a different matter.
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|2:39
|"and" requires both of these to be "true" for this to be executed.
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|2:44
|So we have get "false" here because 1 is not greater than 1.
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|2:51
|We go back to our comparison operators and we will say "if 1 is greater than or equal to 1 'and' 1 equal 1", here we will get "true".
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|3:01
|So now, all I can really think about is to add a few variables in to test this.
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|3:08
|But I am pretty sure that you have got the hang of variables by now, by following my other tutorials.
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|3:12
|So these are the two logical operators.
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|3:17
|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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|3:27
|It is a "login" form. Say a user wants to login to a website.
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|3:34
|You've probably logged into a website before and it said to enter your "username" and "password". Now the keywords are in there.
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|3:40
|We need to check if the users have entered the "username" and the "password".
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|3:44
|If they haven't, there is no point in comparing the "username" to the "password".
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|3:48
|So we can say, for example, "if username and password".
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|3:52
|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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|4:04
|Now I will substitute these. I can say "username" and "password".
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|4:11
|At the moment, this will say "true".
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|4:15
|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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|4:27
|This is going to be okay because we have got both values.
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|4:32
|So let's try it. Yes, that's saying "ok".
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|4:37
|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.
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|4:45
|'You forgot to fill out a field'.
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|4:50
|So if you imagine these are coming from the user - so it's been submitted as you typed your "username" and "password" in.
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|4:57
|We are saying "username" and "password"; basically "username" itself is "true" because it exists...
|-
|5:03
|If you had that inside, that would be acceptable; that would be "true".
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|5:14
|We'll just check that there you go.
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|5:18
|So because we have got "username" and "password" then that's fine.
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|5:23
|But for the 'or' that doesn't really makes sense and you can imagine what will happen.
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|5:28
|So right now, this will equal "true" because we have got both values. So this is 'ok'.
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|5:36
|Now if I go with both of them and try it out.
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|5:42
|"if the username exists" so if the username is "true"...
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|5:46
|At the moment there is no value - so its "false".
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|5:48
|"or the password is true" - that is, the value exists; at the moment it doesn't, so it is "false".
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|5:52
|So we are going to say "You forgot to fill out a field".
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|5:56
|I'll just write here nothing because at the moment it means nothing.
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|6:03
|So refresh and we get nothing.
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|6:05
|So you see, already I have explained how useful these can be in so many every day php applications.
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|6:13
|For example - a form someone can fill in. You will find many other users for it.
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|6:16
|But that's it then.
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|6:19
|Two operators that are logical operators.
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|6:24
|Just try them out and see what all you can do with them.
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|6:28
|I will be using these most definitely in one of my projects quite soon.
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|6:30
|Thanks for watching.
|-
|6:35
|This is Sidharth dubbing for the Spoken Tutorial project.

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PHP-and-MySQL/C2/Logical-Operators/English - Revision history

Pravin1389: moved PHP-and-MySQL/C2/Logical-Operators /English to PHP-and-MySQL/C2/Logical-Operators/English

Chandrika: Created page with '{| border=1 !Time !Narration |- |0:0 |Hello and welcome to a tutorial on "Logical Operators". Its a very brief tutorial but I will keep it like that at the moment. |- |0:09 |I'l…'