Difference between revisions of "PHP-and-MySQL/C2/Functions-Advanced/English-timed"

|Welcome to the Spoken Tutorial on Advanced Function. Here, I'll show you how to create a little calculator program.

|We will deal with a function that allows you to input a value.  Then gain a value out of this, after a mathematical operation

|So, we'll create a function in the same way that we've done before. I'll call this 'calc'

|And I'm going to create my first block . Here , I'll type 'number1', 'number2' and an 'operator'

|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'

|Now inside our function we need to start creating our code. I'm going to create a switch statement inside.

|I'll say switch and put the switch condition or rather the input of the switch is 'op'

|I'll create a block for this and I'll say case = plus then carry out this.

|I'll make a new variable called 'total' which will be equal to 'num1' which is input here plus 'num2'

|I'll break that with a semicolon.  Now there's probability a much easier way to do this by combining the switch statement with a function.  

|So you will be able to use all different kinds of things inside other statements and inside functions.

|So I have created a case for 'plus'. So when this equals to 'plus' supplied by the user, we have 'num1' added to 'num2'.

|Now we need to go down and create another 'case', which is 'minus'. I'll type total = 'num1' - 'num2'

| We will scroll down. Make sure you break that.  

|And here we'll say 'multiply' and we'll say 'divide' and make sure you change the sign here.

|In the default we're going to echo out 'unknown operator'. OK?

|Let me just run through this. Then we will start to call the function.  

|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'.

| As you have probably seen in my mathematical operator - sorry in my arithmetic operator tutorial.

|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.

|If it equals to a 'plus' then we will create a new variable called 'total'.  

|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.

|Now this would do absolutely nothing. Refresh this. Now, if we enter this page, there is nothing, because we haven't called our function.  

|Now to call our function, as you know, we will just say calc and put our values in.

|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 if I refresh this. Nothing. Now why?

|So what we would ideally do is we will echo what has been out put from calc. Now, at the moment this won't do anything if we do a refresh

|We have got nothing, because, there is no return output. So, in each case what we should say is 'return total'.  

|What this does is - If you think of the function as a variable it sets the function's value as the total.

|As long as you say return whatever you say here the function will equal that.  

|So we are going to say return total and we are going to copy that and paste it down for each case.  

|Okay so obviously we don't need to do that for unknown operator. This is because, there is no operator to be found here.

|And we can refresh that.

|You can see the bracket of a function that starts here and ends here

|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

|Okay, we have got a quiet 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.

|And through a switch statement it detects which one and performs the relevant operation to it.  

|An unknown operator error will be given if it can't be determined.

|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.

|This is Sidharth dubbing for the Spoken Tutorial Project. Thanks for watching.