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Introducing Functions
6:52In PHP functions are everywhere. Put simply a function is a way for us to organize and group statements of code. Let's learn how these functions work.
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In PHP functions are everywhere.
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Put simply a function is a way for us to
organize and group statements of code.
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This code can then be wrapped with a name
that will allow us to
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call this same group of code over and
over.
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Functions can be described with the
following analogy.
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A coffee pot would be a function called
make coffee.
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The coffee pot takes coffee grounds and
water.
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Then it heats the water and pours the
water over the coffee,
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finally, through a filter, returning a cup
of liquid coffee.
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Functions in most cases will be returning
a value based off of supplied input,
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such as arguments, known values,
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like databases, external APIs, or date and
time.
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To start with we're gonna open up a
standard set of PHP tags,
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just like we're used to in all the
previous lessons.
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Then we're going to use a new keyword
called function.
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The keyword function will signal the PHP
interpreter to tell it
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that anything after this is going to be a
function.
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The next thing we pass after function, is
a word hello,
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which is the name of our function.
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We open and close parentheses, and then we
open and close our curly braces.
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Now inside of these curly braces,
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we're gonna do some sort of statement,
some sort of PHP work.
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In this case, we're going to simply echo a
string, and the string is Hello, World!
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Make sure you close it with a semicolon,
and then we move on to the next step.
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This is the way we call our function.
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See, in order to call the function,
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we just simply place the name on a line by
itself.
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And then open and close parentheses to let
the interpreter know that
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we're calling a function named hello.
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We'll close that statement with a
semicolon, and
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then the output, when this is run should
be, Hello, World!
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All right, so in our workspace here we
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have an index.php with a PHP tag opened up
for us to start with.
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So to create a function we're going to
start by using the keyword function.
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So go down a line and type function, all
right, followed by the function name.
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And in this case we'll call our function,
hello.
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All right, we're gonna open and close the
set of parentheses.
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There aren't gonna be any arguments, we'll
get into that a little bit later.
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Then open and close our curly braces.
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Now anything inside of here,
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is what's going to happen when we call the
function hello.
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So we'll tab in and echo a statement.
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So do echo and Hello, World!
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And close it with another single quote in
the string and
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then a semicolon to end the line.
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Now that will actually create our function
for
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us, but in order to use the function we
have to call the function.
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So in order to call a function,
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we simply type the function's name
followed by parentheses.
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So we'll type in hello, and then open and
close parentheses.
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Now it is PHP,
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so we're gonna need to close this line
with a semicolon to end the statement.
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Okay, let's go ahead and
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save this, and then we will ease on over
to the eyeball for preview.
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And we will see now that it says hello
world, which is exactly what we want.
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All right, let's switch back over to our
code and we will create a new example.
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I'm gonna actually go ahead over and
remove the line 7.
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We don't want to call it.
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We're gonna create another function, and
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this function is going to be called
is_Mike.
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So let's say we'll do a function.
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And then is_Mike.
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Open and close parentheses, and open and
close our curly braces.
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So in here, the idea behind this function
is we're gonna have a variable.
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And that variable would be say, the
currently logged in user.
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We'll call that variable current user.
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Now, in order to test to test to see if
it's Mike,
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we're gonna need to bring in current user,
and then do an if statement, and
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then output a string that tells us whether
it is or is not Mike.
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So let's do that with starting with a
conditional function, so,
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or a conditional if statement.
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So I'll do if, and then we'll say our
variable is current_user, so
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current and underscore user.
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Equals, equals to make sure it's
equivalent.
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And then, Mike.
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We'll close that with a single quote.
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Close our parentheses and now we have a
completed if statement.
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If the current user is equal to Mike,
we're gonna wanna output a string.
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So I'll do echo, and I'll say, It is Mike.
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All right.
Close the single quote and
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then close the statement with a semicolon.
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So now if current_user is equal to Mike
then we'll have a echo statement that
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says, It is Mike.
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Otherwise, so we need an else statement
here and inside of our else statement,
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we'll say, it is not Mike.
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So, echo.
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Nope, it is not Mike.
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All right.
I'll put a period in here, and
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then a semicolon to close the line.
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Now this is great, except when we call it,
so we'll go is_mike.
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The only problem here is that we don't
have a variable called, current_user.
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Now, there's something you need to
understand about function scope.
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Any kind of variable that's used inside of
the function here,
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so inside between lines 10 and line 14,
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anything inside that function is only for
that function.
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So, in order to get something from the
outside,
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we have to pass that through as an
argument, or
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we can use the global statement, which
we're gonna do now because we're gonna use
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something outside of the function scope,
but we're not into arguments just yet.
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So, let's create this variable,
current_user, and
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that current_user variable is gonna be
equal to, to start off with, Mike.
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All right, now to get that inside of our
function.
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We're gonna need to go inside the function
and type global as our keyword, and
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then current_user.
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All right, now that will tell us we have a
global variable outside of the function
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scope called current_user that we would
like to use inside of our function.
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Okay, now that we've done that,
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let's run this code by going to our
preview and see what it looks like.
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So I'm gonna go over to our, preview after
I've saved it and then hit Refresh.
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It is Mike, which is correct.
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Now if we changed current_user to say, me,
and then saved it,
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and then went back over and refreshed.
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It'll say Nope, it is not Mike.
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So now we have a function that runs,
simply from a single line that we
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can find out whether or not the current
user is equal to Mike.
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