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In 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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[MUSIC]
0:00
In PHP functions are everywhere.
0:04
Put simply a function is a way for us to
organize and group statements of code.
0:07
This code can then be wrapped with a name
that will allow us to
0:12
call this same group of code over and
over.
0:15
Functions can be described with the
following analogy.
0:18
A coffee pot would be a function called
make coffee.
0:22
The coffee pot takes coffee grounds and
water.
0:25
Then it heats the water and pours the
water over the coffee,
0:28
finally, through a filter, returning a cup
of liquid coffee.
0:31
Functions in most cases will be returning
a value based off of supplied input,
0:35
such as arguments, known values,
0:40
like databases, external APIs, or date and
time.
0:42
To start with we're gonna open up a
standard set of PHP tags,
0:47
just like we're used to in all the
previous lessons.
0:51
Then we're going to use a new keyword
called function.
0:54
The keyword function will signal the PHP
interpreter to tell it
0:57
that anything after this is going to be a
function.
1:02
The next thing we pass after function, is
a word hello,
1:05
which is the name of our function.
1:08
We open and close parentheses, and then we
open and close our curly braces.
1:11
Now inside of these curly braces,
1:16
we're gonna do some sort of statement,
some sort of PHP work.
1:18
In this case, we're going to simply echo a
string, and the string is Hello, World!
1:22
Make sure you close it with a semicolon,
and then we move on to the next step.
1:28
This is the way we call our function.
1:32
See, in order to call the function,
1:35
we just simply place the name on a line by
itself.
1:36
And then open and close parentheses to let
the interpreter know that
1:40
we're calling a function named hello.
1:43
We'll close that statement with a
semicolon, and
1:45
then the output, when this is run should
be, Hello, World!
1:48
All right, so in our workspace here we
1:52
have an index.php with a PHP tag opened up
for us to start with.
1:57
So to create a function we're going to
start by using the keyword function.
2:01
So go down a line and type function, all
right, followed by the function name.
2:06
And in this case we'll call our function,
hello.
2:13
All right, we're gonna open and close the
set of parentheses.
2:16
There aren't gonna be any arguments, we'll
get into that a little bit later.
2:20
Then open and close our curly braces.
2:23
Now anything inside of here,
2:26
is what's going to happen when we call the
function hello.
2:28
So we'll tab in and echo a statement.
2:31
So do echo and Hello, World!
2:34
And close it with another single quote in
the string and
2:39
then a semicolon to end the line.
2:44
Now that will actually create our function
for
2:46
us, but in order to use the function we
have to call the function.
2:49
So in order to call a function,
2:54
we simply type the function's name
followed by parentheses.
2:55
So we'll type in hello, and then open and
close parentheses.
2:59
Now it is PHP,
3:03
so we're gonna need to close this line
with a semicolon to end the statement.
3:04
Okay, let's go ahead and
3:09
save this, and then we will ease on over
to the eyeball for preview.
3:09
And we will see now that it says hello
world, which is exactly what we want.
3:14
All right, let's switch back over to our
code and we will create a new example.
3:20
I'm gonna actually go ahead over and
remove the line 7.
3:24
We don't want to call it.
3:28
We're gonna create another function, and
3:29
this function is going to be called
is_Mike.
3:32
So let's say we'll do a function.
3:35
And then is_Mike.
3:37
Open and close parentheses, and open and
close our curly braces.
3:41
So in here, the idea behind this function
is we're gonna have a variable.
3:46
And that variable would be say, the
currently logged in user.
3:50
We'll call that variable current user.
3:53
Now, in order to test to test to see if
it's Mike,
3:55
we're gonna need to bring in current user,
and then do an if statement, and
3:58
then output a string that tells us whether
it is or is not Mike.
4:01
So let's do that with starting with a
conditional function, so,
4:05
or a conditional if statement.
4:09
So I'll do if, and then we'll say our
variable is current_user, so
4:12
current and underscore user.
4:16
Equals, equals to make sure it's
equivalent.
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And then, Mike.
4:21
We'll close that with a single quote.
4:22
Close our parentheses and now we have a
completed if statement.
4:23
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.
4:32
All right.
Close the single quote and
4:38
then close the statement with a semicolon.
4:40
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.
4:47
Otherwise, so we need an else statement
here and inside of our else statement,
4:49
we'll say, it is not Mike.
4:54
So, echo.
4:55
Nope, it is not Mike.
4:57
All right.
I'll put a period in here, and
5:03
then a semicolon to close the line.
5:05
Now this is great, except when we call it,
so we'll go is_mike.
5:07
The only problem here is that we don't
have a variable called, current_user.
5:14
Now, there's something you need to
understand about function scope.
5:19
Any kind of variable that's used inside of
the function here,
5:22
so inside between lines 10 and line 14,
5:27
anything inside that function is only for
that function.
5:32
So, in order to get something from the
outside,
5:36
we have to pass that through as an
argument, or
5:39
we can use the global statement, which
we're gonna do now because we're gonna use
5:42
something outside of the function scope,
but we're not into arguments just yet.
5:46
So, let's create this variable,
current_user, and
5:50
that current_user variable is gonna be
equal to, to start off with, Mike.
5:54
All right, now to get that inside of our
function.
6:00
We're gonna need to go inside the function
and type global as our keyword, and
6:04
then current_user.
6:09
All right, now that will tell us we have a
global variable outside of the function
6:12
scope called current_user that we would
like to use inside of our function.
6:16
Okay, now that we've done that,
6:21
let's run this code by going to our
preview and see what it looks like.
6:22
So I'm gonna go over to our, preview after
I've saved it and then hit Refresh.
6:26
It is Mike, which is correct.
6:32
Now if we changed current_user to say, me,
and then saved it,
6:35
and then went back over and refreshed.
6:40
It'll say Nope, it is not Mike.
6:43
So now we have a function that runs,
simply from a single line that we
6:44
can find out whether or not the current
user is equal to Mike.
6:48
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