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

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

|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 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.  

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

|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?

|So, what we would 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'''.

|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.

|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.

|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.