Beginner PHP Tutorial - 192 - Changing a Property Value Video Lecture | PHP for Absolute Beginners: From Novice to PHP Master - Web Development

hi this is Alex from PHP academy' natal
back with another PHP tutorial for the
new Boston in the last object-oriented
programming example we looked at we
created a class called bank account with
a property of balance and we've set this
to 10.5 just as an example we've made
this public for now before we talk about
properties and their different types we
just create it public so that can be
used by the rest of our page now we've
also created a method which is called
display balance and we've echoed this
out here you can see it returns a value
here of balance and then this this
balance so we're returning the the value
of the balance which we've now echoed
out onto the screen but what happens if
we want to start to modify this balance
so within a bank account you can
obviously display your balance what you
can withdraw and you can add funds to
your account so you can you can add
money so we can go ahead and we can
create another method and we'll name
this first and then we'll talk about how
we're going to do it so we're going to
say public function withdraw and we're
going to create the skeleton so we've
got our parentheses here and then we've
got our curly brackets here as well
so within withdraw what we want to do is
much like a function in normal like
proceed when your program procedurally
in PHP we want to take in a parameter so
I'm going to take in int or amount for
example that makes it look a bit better
so we have a function now which is
called a methods I'm going to be calling
the methods called withdraw and with
this withdraw method we can specify a
specific amount of money that we want to
withdraw so let's go ahead and start the
calculation now what we want to do is we
don't want to return a value to the user
because our balance will return a value
our withdraw is going to do everything
in the background to withdraw the funds
from the bank account so what we can now
do is we can say this remember we use
the this keyword or the variable if you
like to which then
I mean the variable this corresponds to
the whole of our class so we're saying
this balance so we're picking up the
variable here much like we did in this
part here and then we're saying equals
this balance now this is equivalent and
then we say minus the amount
so we're taking the parameter that we've
fed in on the argument that we fed in
the argument here and when my nursing so
we're using the minus the minus
mathematical arithmetic operator here to
minus the amount that we specify so this
is the same as if we were going to do
balance oh sorry
balance equals balance minus amount
however because we're working within a
class we need to reference it this and
then we use the hyphen and the greater
than sign to get the balance from this
class so the current balance of the
current balance which is a property
inside this class is equal to the
current balance minus amount so what
we've done here is we've successfully
created a method that is going to
withdraw a specific amount from our bank
account so let's say before we display
our balance we want to withdraw a
certain amount so withdraw a certain
amount is obviously going to take away
an amount from our balance so let's go
ahead and do this and then we're just
going to touch up this method to ensure
that we can't withdraw any more than we
actually have in our bank account so we
simply say Alex remember we've created
the new instance of the variable R the
class up here we say Alex and then we
say withdraw and then obviously in the
brackets much like we did with display
data we didn't put anything in the
brackets because there's no arguments in
here with withdraw we just specify an
integer amount so we could say withdraw
five so if we want to withdraw five
pounds we withdraw it this what this
will do is it will take away 5 from the
property balance and then it will echo
out our balance so we're displaying our
balance so let's just go ahead and
comment this so we know what we're doing
new instance of class then what we're
doing is withdrawing five pounds and
then we're displaying balance so what
we've done is create a new instance
which is fine now what we've done the
difference is before we display the
balance we're making withdrawal of five
so let's go back now what should happen
is we should display the balance out as
five point five as you can see here so
we've displayed the balance out and out
now as five point five so we've
successfully withdrawn five pounds from
our bank account in fact I'm going to
get rid of these comments and that's
going to make it look a lot Messier okay
so now what we need to do is check
inside withdraw whether whether we can
withdraw this money or not so what we
need to do is we need to create an if
statement we need we need to say if this
balance and we can put that in brackets
just to make it easier to read if this
balance is smaller than the amount so if
our balance is smaller than the amount
we're trying to withdraw then all no
sorry we need to say echo something
otherwise we can make the deduction from
our bank account okay so in here we can
just say echo or we can even throw a new
exception but we'll deal I have to
Taurus on throwing exceptions so you can
take a look about so we've got just echo
not enough funds or money also to keep
things simple so let's go back and
refresh and we can see that that's
absolutely fine now let's try and
withdraw 12 pounds so let's go down so
we're going to say withdraw 12 pounds
now what we should do is get the error
message
not enough money and then it's still
displaying our balance because we've
specified you specify that displaying
our balance down here so not enough
money now we can create this error in
many different ways however for now I'm
just going to echo this out just to keep
things simple so what we've done in this
tutorial let's just briefly recap we
have created a new method called
withdraw and we've allowed the user to
withdraw a certain amount of money from
their bank account using this amount
argument we're checking of the there's
enough money in the account first of all
otherwise we're deducting the balance
from the balance property or the amount
withdrawn from the balance property and
we're doing this by calling the method
here which is reference to the new
instance of the bank account class
that's named Alex