PHP-and-MySQL/C2/Functions-(Advanced)/English

Time	Narration
0:0	Welcome to the Spoken Tutorial on Advanced Function. Here, I'll show you how to create a little calculator program.
0:04	We will deal with a function that allows you to input a value. Then gain a value out this, after a mathematical operation
0:13	So, we'll create a function in the same way that we've done before. I'll call this 'calc'
0:19	And I'm going to create my block first. Here inside, I'll type 'number1', 'number2' and an 'operator'
0:28	Now this will be a numerical value. This will be an integer or decimal, depending on the user-input. This will also be the same and this will be the string value of either 'add' 'subtract' 'multiply' or 'divide'
0:44	Now inside our function we need to start creating our code. I'm going to create a switch statement inside.
0:54	I'll say switch and put the switch condition or rather the input of the switch is 'op'
1:03	I'll create a block for this and I'll say case = plus then carry out this.
1:14	I'll make a new variable called 'total' which will be equal to 'num1' which is input here plus 'num2'
1:28	I'll break that with a semicolon. Now there's probably a much easier way to do this by combining the switch statement with a function.
1:39	So you will be able to use all different kinds of things inside other statements and inside functions.
1:45	So I have created a case for 'plus'. So when this equals to 'plus' supplied by the user, we have 'num1' added to 'num2'.
1:57	Now we need to go down and create another 'case', which is 'minus'. I'll type total = 'num1' - 'num2'
2:10	We will scroll down. Make sure you break that.
2:16	We'll now copy this code down.
2:20	Here we'll say 'multiply' and here we'll say 'divide' and make sure you change the sign here.
2:27	Now if you don't understand what is going on here please feel free to contact us via e-mail. I hope every probable confusion will be resolved in that way.
2:36	In the default we're going to echo out 'unknown operator'. OK?
2:45	Let me just run through this. Then we will start to call the function.
2:50	I have got a function called calculator or calc for short, which takes a number as input, then a second number and then an operator which can either be 'plus' 'minus' 'multiply' or 'divide'.
2:58	As you have probably seen in my mathematical operator - sorry in my arithmetic operator tutorial.
3:14	Now we have a switch statement inside, which takes this 'op' into account. It takes what has been entered. Now if it equals to a 'plus', remember that it switches over to this statement. It is easier to write and is much more efficient.
3:32	If it equals to a 'plus' then we will create a new variable called 'total'.
3:39	That's going to be equal to the first number which was entered and added to the second number which was entered.
3:45	Here we will say if it's a 'minus', then the variable 'total' - okay remember, the variable 'total' will only be set once for each case either plus or minus - so this total variable going to be number 1 - number 2 and the same for multiply and divide as well.
4:10	Now this would do absolutely nothing. Refresh this. Now, if we enter this page, there is nothing, because we haven't called our function.
4:20	Now to call our function, as you know, we will just say calc and we will put our values in.
4:25	Let's us just give it two numbers say 10 and 10 and a 'plus' . Okay, so that will be 20. Now watch what happens when I refresh this. Nothing. Now why?
4:45	The reason is that we haven't echoed this out. We've just set it as a variable.
4:50	So what we would ideally do is we will echo what has been out put from calc. Now, at that moment this won't do anything if we do a refresh
5:00	We have got nothing, because, there is no return output. So, in each case what we should say is 'return total'.
5:16	What this does is - If you think of the function as a variable it sets the function's value as the total.
5:26	As long as you say return whatever you say here the function will equal that.
5:31	So we are going to say return total and we are going to copy that and paste it down for each case.
5:42	Okay so obviously we don't need to do that for unknown operator. This is because, there is no operator to be found here.
5:49	And we can refresh that.
5:49	We still don't have anything. Guess why?
5:55	The reason this is not working is because I've echoed this inside a function. That's a mistake.
6:03	You can see the bracket of a function that starts here and ends here
6:08	I'll place this underneath here, where it should be and then refresh it. It is 20 okay, so we can see the 10 + 10 is 20 through our function
6:24	So let's pick some different values, say, 13 and 7 and divide. Let's see what we get.
6:35	Okay, we have got a quiet long decimal number. So you can see that this is quite a good function that we have made. We have got our first number, our second number and an operator.
6:46	And through a switch statement it detects which one and performs the relevant operation to it.
6:54	An unknown operator error will be given if it can't be determined.
6:58	So, for example let's take 'a' which is not a valid operator. As soon as we refresh it's going to unknown operator. This brings us to the end of the tutorial on advanced functions. We saw that we can input a value and then returned a value echoing out using a return command.
7:13	This is Sidharth dubbing for the Spoken Tutorial Project. Thanks for watching.

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