Beginner PHP Tutorial - 74 - Unsetting PHP Sessions Video Lecture | PHP for Absolute Beginners: From Novice to PHP Master - Web Development

hi this is Alex from PHP academy' dog
with another video for the new Boston
now we've already looked at setting PHP
sessions and why they're useful however
if we wanted to unset a session for any
reason or unset a particular session or
unset all sessions we need a way to do
this and there's a couple of ways that
you can do this either by unsetting an
individual session you might not want to
end all your sessions but we can we've
got a function called unset that's going
to unset a particular session that we
specify or you can use another function
called session destroy' which will unset
all the sessions related to that user
and your server so in this set dot PHP
file we've already started up our
session and we've and we've set a
session called username to the value of
Alex and in the view we're checking for
this now I'm going to create a new file
and I'm going to call this an unset PHP
now this might be a logout file you
might be logging your users out we've
already spoken about why sessions might
be useful for login systems we might be
even clearing the total of a user's
basket or deleting items from a user's
basket so just imagine this is a logout
page now you may for example want to
unset a particular session now to do
this you want to use unset now you can
see that the the session is called
session or it's called user name so I'm
going to unset dollar underscore session
user name now there's a fundamental
mistake I've made in this file on
purpose just so you can see why now
let's go ahead and set this I'm going to
go back and I'm going to click on View
and you can see that it's welcoming me
here so we've already looked at this
example now if I'm to click on unset PHP
and then go back and then click on view
again you can see that it still says
welcome Alex
now why is this the case when we've used
this unset feature or this function to
unset this username and the simple
answer is I've actually purposely for
Center per session star so even though
your unsetting sessions you still need
to declare this function or call this
function in order to unset your sessions
and it with the same for the other
example I'm going to show you in just a
moment so let's go back and click set
just to make sure that's definitely set
click on view and it says welcome Alex
so now let's go back and click on unset
now this time we should have succeeded
in unsetting that session so if we click
on view analysis please log in so you
may come across in your programs when
you're using this oh that the sessions
not unsetting you know why is this this
might be a question in your mind why
isn't it working it's it's frustrating
you the answer is always check that
you've correctly started your sessions
up before you try to unset them now what
if I want to have a couple of sessions
that I want to I want to unset so I want
to unset more than one session in fact
all the sessions that exist so I'm going
to make a few changes to this program
under set I'm going to set another
session and this is going to be called
age and I'm going to set this equal to
21 now on view we're going to say if is
sept session username and dollar
underscore note remember another another
intercept function in there so we're
checking that both these sessions exist
and then we're saying welcome to the
username and then we're going to say you
are and then we're going to specify my
age just by cooling that in there or
concatenate in that so now what's the
result we're going to achieve if we come
and reset our sessions and we come back
and click view welcome Alex you are 21
so we've used two different sessions now
now what I'm going to do is I'm going to
click on set I'm going to go back again
and click on View in fact this is a bad
example because we're checking for both
of these let's just
get rid of that there okay so now if i
refresh you can see welcome and then a
common than a full stop because just one
of the sessions is missing remember in
this unset file we're only unsetting the
username so let's just reset everything
again so we can view the example of
unsetting all of them click view so now
this has been displayed correctly now
what happens if I want to unset all
sessions so I'm going to get rid of this
line and I'm simply going to type
session underscore destroy now what this
command here is going to do when we call
this function we are sunsetting all
sessions that are currently that
currently exist so not for all users
across your website but just between the
connection me and the server so now what
I can do is I'm going to refresh again
just so you can see that the data is
still there now I'm going to click unset
I'm going to get back again I'm going to
click view and we've removed both the
session data so we remove my name and my
age so that's basically unsetting
session data in PHP