Beginner PHP Tutorial - 33 - Global Variables and Functions Video Lecture | PHP for Absolute Beginners: From Novice to PHP Master - Web Development

hi this is Alex from PHP academy' de org
and this is another video tutorial for
the new Boston now in this tutorial I'm
going to be talking about global
variables and using them inside
functions now you may come across the
problem that when you're pre defining
variables outside of your functions and
you're trying to use them within your
functions you might find that you're not
getting any sort of response from this
your the variable will not you know you
might be able to do anything with it so
let's use the example with an IP address
let's create the user's IP address
inside a variable so we're going to say
structure it like this now don't worry
if you don't understand this code if
you've never seen this part of the code
before all this does is it returns the
user's IP address server it's just a
preset of environmental variables that
we can use so let's just echo this out
as it is and then we'll see about
creating a function that's going to do
something with this IP address what
we're going to just be doing is echoing
it out but we're going to be doing that
inside a function so let's refresh now
because I'm on a local on my local host
local server I'm working on my computer
my IP address is just 1.1 27.0 dot 0 dot
1 which is the standard notation for a
local server now what happens if I
create a function down here let's say an
echo IP and inside here I just want to
echo out use
now you can imagine in a normal program
that you've created however simple or
complex it's going to be wherever you
echo this variable out or wherever you
do something with this variable for
example we might say um let's say string
equals your IP address is
and then we can catenate the user IP on
the end of their let's just use this
outside the function first of all or you
can keep that in the X we're not going
to call the function yet let's just use
this outside of here and we can yet just
echo that out so let's have a look at
what it says so we've got your IP
address is and then it gives us the IP
address let's just put a space there
okay so this works you would expect it
to work because you've referenced the
variable here okay so now what happens
if we do this inside a function so I've
created the string your IP address is
and then I'm going to echo out the
string so what you'd expect to happen is
for the variable here to be put into
here so that will make up this string
and then we're echoing out the string so
let's refresh the page and see what
happens
okay so we haven't actually called our
function so that's one vital thing I
forgot so I'm calling the function down
here so presumably once we call the
function the two lines of highlighted in
blue will be run so let's try this out
okay now you'll notice that the string
itself has actually been echoed out
however the user IP has not but for
example if we echo it out out here it
still does exist so we're still echoing
out this variable still you know holds a
value however what's happening here is
we're not being able to access it inside
this function and there's one simple
line of code that you can use to do this
and you can put multiple variables
within this but now we're just going to
be working with one so all we need to do
is specify the global keyword and then
reference the variable number that we
want to make global to this function so
global user IP now what will happen is
this variable will be able to be picked
up from out here and then therefore it
will be put into there let's refresh and
you can see that it works
we are echoing out this string the user
IP has been gained from this value here
like I said you can do multiple
things so if you had say another
variable here and another one here you
can just separate them by commas so why
would we need to do this the answer is
simple you might have lots of either
static or dynamic variables that you
have to define outside for example you
might have to define it in an include
file you might be including a different
file that contains this user IP so to be
able to use it inside your function you
want to create it and globally first in
inside your function and then it will be
able to be used so for example this IP
this IP address situation we might want
to define it somewhere else we might not
want to define it within our function
because you could in fact just to find
it inside and it would still that's just
right it would still work so we're still
getting exactly the same result from
this when we refresh however what
happens if we want to use this user IP
now outside the function we're going to
have to declare it again so it's a waste
of you know declaring a function inside
the function at outside so we tend to
just use the notation that I've
explained and that will allow your
outsider phone function variable to be
used within