Beginner PHP Tutorial - 138 - Logging the User In Part 3 Video Lecture | PHP for Absolute Beginners: From Novice to PHP Master - Web Development

so we need to continue in login form to
actually log the user in so how are we
going to do this first of all we need a
query and this is going to be equal to
select and we need to select the
username user name and password from and
that lets go reference back to our table
to see from users so it's selecting from
users where and then we're going to say
username is equal to username and
password is equal to password so we've
constructed here a query where we're
selecting the username and password in
fact we don't even need to do that let's
just select the ID so we're selecting
the ID from our users table where the
username is equal to Alex in this case
and the password is equal to password in
this case now we've got one problem
already password is plain text and the
password stored in the database is md5
data so what we need to do here is we
need to say md5 wrapping around password
which will then automatically convert
this to an md5 value in fact now that's
not going to work I'll tell you why if
the user entered nothing we're still
generating an md5 hash so we can get
away with not entering a password so
instead of doing that let's create a new
variable which is probably better called
password hash and that's going to equal
to md5 of password so we create a new
variable now we can pop this into our
query like that so let's first of all
execute this query so query run equals
MySQL Oh query query and let's pop this
into an if statement just to check that
it works so if that then run this block
otherwise something now we've actually
now predetermined so if this query is
fine and it works then we can in fact me
we don't need this else here
if this query works then we can do
something with it and what we need to do
with it is we need to check how many
rows have been returned now
if 0 rows have been returned we have if
0 rows been returned a username and a
password don't match so we use name and
password combination haven't matched
which means they may have entered the
correct username they may have not
entered the correct password or
vice-versa they may have kren to the
correct password but not the right
username so we need to create a check in
here first of all we'll say at query
none and that's call num rows would be
better and that's equal to MySQL num
rows of our query that we've run and now
we need to perform a check to say if
query num rows is equal to 0 no such
user exists otherwise do something else
so here we're going to say echo invalid
invalid username password combination
okay so we've executed our query as long
as the query is structured properly and
it makes sense we're going to continue
with this code here then we're creating
a value of the number of rows returned
then we're checking if that equals to 0
if it does equal to 0 it means that the
username and password combination don't
match so we echo out a warning to the
user and we don't lock them in otherwise
we need to say
okay for now the users logged in
successfully so let's use this as an
example so let's go back to our users
table we've got Alex in the password
which i think is past one yet past one
two three but the md5 hash remember we
convert the md5 hash automatically when
we process the login and then we have
various bits of information which aren't
important just now so let's try a user
login that's incorrect so I'm going to
type Billy and pass one two three now by
mine the pass one two three one two
three
exists in the database but it doesn't
exist next to Billy so let's click login
we've got invalid username password
combination so our SQL query was
structured correctly but it returns no
rows now otherwise we want to say if
query num rows equals 1 then we can echo
ok because we're never going to echo two
rows because the username is not going
to exist twice we're not going to have
users on our website with the same
username so now let's try this with Alex
and pass on I think I typed pass yet
pass one two three and click login and
it says ok so now let's return some of
the data that we've been processing so
we can make sure that we network we
already know it matches let's echo out
username and will echo out and I will
just echo out the password hash so you
can see how this is working
so once we've logged in correctly a user
name and pass one two three you'll see
that this is the hash the password hash
of what we've entered which is starts
with three to two and ends with a 24 so
three to two a 24 so we know that it's
converted the hash properly we know that
anyway so
now that the users logged in okay and
we've displayed this okay message we
don't actually want to do this this was
just for our purpose what we now want to
do is we want to set a session with the
users ID so we've selected the ID from
the database but now we need to get this
data so I'm going to say user underscore
ID and this is going to equal to MySQL
result remember this function from when
we learn specifics on using databases
MySQL result we're taking the result
from the query that we run earlier we're
going for row zero and we're looking in
the ID column so let's just echo out
user ID so we know this works properly
let's test now with adding another user
so we can see if this ID is returned
correctly for each user we login