PHP-and-MySQL/C2/Functions-Advanced/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:03 | Welcome to the Spoken Tutorial on Advanced Functions. Here, I'll show you how to create a little calculator program. |
| 00:11 | We will deal with a function that allows you to input a value, then gain a value out of this after a mathematical operation. |
| 00:20 | So, we'll create a function in the same way that we've done before. I'll call this 'calc'. |
| 00:27 | And I'm going to create my first block . Here, I'll type 'number1', 'number2' and an 'operator'. |
| 00:35 | 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'. |
| 00:52 | Now, inside our function we need to start creating our code. I'm going to create a switch statement inside. |
| 01:00 | I'll say switch and put the switch condition or rather the input of the switch is $op. |
| 01:09 | I'll create a block for this and I'll say case "+" (plus) then carry out this. |
| 01:18 | I'll make a new variable called $total which will be equal to 'num1' which is input here plus 'num2'. |
| 01:32 | I'll break that with a semicolon. Now there's a probability, a much easier way to do this by combining the switch statement with a function. |
| 01:44 | So, you will be able to use all different kinds of things inside other statements and inside functions. |
| 01:52 | So I have created a case for 'plus'. So when this equals to 'plus' supplied by the user, we have '$num1' added to '$num2'. |
| 02:03 | Now we need to go down and create another case which is 'minus'. I'll type $total = $num1 - $num2; |
| 02:17 | We will scroll down; make sure you break that. |
| 02:21 | We'll now copy this code down. |
| 02:24 | And here, we'll say "*" (multiply) and we'll say "/" (divide) and make sure you change the sign here. |
| 02:34 | Now if you don't understand what is going on please feel free to contact us via e-mail. I hope every confusion will be resolved in that way. |
| 02:45 | In the default, we're going to echo out "Unknown operator". OK? |
| 02:51 | Let me just run through this. Then we will start to call the function. |
| 02:56 | 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 could be either 'plus' 'minus' 'multiply' or 'divide'. |
| 03:12 | As you have probably seen in my mathematical operator - sorry in my Arithmetic Operator tutorial. |
| 03:20 | 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 much more efficient. |
| 03:42 | If it equals to a "+" (plus) then we will create a new variable called 'total'. |
| 03:48 | That's going to be equal to the first number which was entered and added to the second number which was entered. |
| 03:56 | 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 number1 - number2 and the same for multiply and divide as well. |
| 04:21 | Now this would do absolutely nothing. Refresh this. Now, if we enter this page, there is nothing because we haven't called our function. |
| 04:33 | Now to call our function, as you know, we will just say calc(); and put our values in. |
| 04:40 | Let us just give it two numbers say 10 and 10 and a "+" (plus). Okay, so that will be 20. Now watch what happens if I refresh this. Nothing. Now why? |
| 04:55 | The reason is that we haven't echoed this out. We've just set it as a variable. |
| 05:01 | So, what we ideally do is, we will echo what has been output from calc. Now, at the moment this won't do anything if we do a refresh. |
| 05:11 | We have got nothing because there is no return output. So, in each case, we should say return $total;. |
| 05:24 | What this does is - if you think of the function as a variable, it sets the function's value as the $total. |
| 05:32 | As long as you say return, whatever you say here, the function will equal that. |
| 05:39 | So, we are going to say return $total and we are going to copy that and paste it down for each case. |
| 05:47 | Okay. So, obviously we don't need to do that for "Unknown operator". This is because there is no operator to be found here. |
| 05:58 | And we can refresh that. |
| 06:00 | We still don't have anything. Guess why? |
| 06:04 | The reason this is not working is because I've echoed this inside a function. That's a mistake. |
| 06:10 | You can see the bracket of a function that starts here and ends here. |
| 06:15 | I'll place this underneath here where it should be and then refresh it. It's 20. okay, we can see the 10 + 10 is 20 through our function. |
| 06:37 | So let's pick some different values, say, 13 and 7 and divide. Let's see what we get. |
| 06:46 | Okay, we have got a quite long decimal number. So you can see that this is quite good function that we have made. We have got our first number, our second number and an operator. |
| 07:00 | And through a switch statement, it detects which one and performs the relevant operation to it. |
| 07:06 | An "Unknown operator" error will be given if it can't be determined. |
| 07:11 | 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. |
| 07:31 | This is Sidharth, dubbing for the Spoken Tutorial Project. Thanks for watching. |
