Beginner PHP Tutorial - 23 - Logical Operators Video Lecture | PHP for Absolute Beginners: From Novice to PHP Master - Web Development

hello this is Alex from PHP academy' de
org and this is a video tutorial for the
new Boston in this video I'm going to be
talking about logical operators now
we've already seen examples of
comparison operators arithmetic
operators and assignment operators so
we've assigned variables we've compared
them now what happens if we want to use
a bit of logic to maybe say want to
check a few variables at once if they
compare two different values now the
best way to explain this is to create an
example so if I was to create a number
here number one equals ten now what I
want to do is I want to create an if
statement here the block and inside here
I want to say number one greater than or
equal to ten now echoing out this would
be true
so we valuated this to true number one
is equal to ten so when we refresh in
our browser we get true echoed out
however let's say we want to check at
saying an upper and a lower bounds we've
already seen examples like this where
we've we've simply made a comparison
check but let's apply some logic into
this I'm going to create a variable
called upper and this is going to be a
thousand and my lower is going to be 500
I'll make sure we assign that there my
lower limit is going to be 500 now what
I want to do is I want to let's change
this text to let's say okay I want to
test whether a specific number supplied
which could be up here is equal or it's
between a thousand and five hundred so I
want this number to be either 1500 or
somewhere in between so it could be five
hundred and five or it could be 999.9
it could be a thousand it could be five
hundred but it can't be under five
hundred so it can't be four nine seven
or it can't be one thousand
and one for example so this number at
the moment is one let's put it in within
our boundaries so I'm going to say 654
which is between 500 and 1000 now how
are we going to make this check now in
PHP we have logical operators we have
and we have or or we have not now I'm
not going to discuss the knot in this
tutorial in depth and I might come into
it but we're definitely going to be
discussing the and or the or now and or
can be written in a few ways we can
write and like this with a double
ampersand symbol or we can write it and
you can see it's turned blue as well it
doesn't have to be in capitals but it
just makes everything easier to see or
is either two vertical lines they're
also known as pipes so they're on your
keyboard or you can just simply you
probably guessed right or so we need to
think logically and we need to think in
plain English a lot of the time whenever
we program anything so I need to say
does this nut is this number greater
than or equal to 500 which is the lower
variable and is it less than or equal to
upper so you probably guessed let's
start writing this out and speaking in
English as we go so I'm going to say if
number is greater than or equal to lower
and so let's space this out there and
number is less than or equal to upper so
it has to be greater than or equal to
500 and it has to be less than or equal
to foot to a thousand so in this case
will echo out okay if that's the case so
let's refresh and see what happens
okay we're left with the well we're
printing out or echoing out okay so what
happens if we now change this number to
nine nine nine point nine nine
for example let's refresh we're still
being produced in our browser with okay
it's still telling us it's okay so this
statement is still evaluating to true
now what happens if we say let's just
say 10,000 okay
so or 10,500 this is obviously greater
than a thousand so we should be left
with the alternative which will be to
display nothing's we don't have our else
on the end so if we refresh you can see
nothing's displayed so this has worked
really really well what I'm going to do
at this point is I'm just going to use a
bit of concatenation inside here and I'm
going to say number must be between
space lower and then I'm going to
concatenate on some text and with a
space either side and upper okay so this
is going to read number must be between
lower and upper in fact no that needs to
go in our else part obviously because if
that doesn't evaluate to true otherwise
okay
okay so the way it works is that if this
evaluates to true was hanging okay
otherwise we're telling the user the up
the lower in the upper bounds of the
number so if we refresh so far number
must be between five hundred and a
thousand if we pop this straight in the
middle and say 750 it's telling us this
okay so let's go and say that - thousand
- 100 for example number must be between
500 and a thousand and then we can do
the inclusive numbers as well so if it's
500 it's going to be still okay let's
say we were to take the equals out of
there remember it now doesn't equal so
it's working so maybe we could put a
little message on the end of here saying
inclusive Okaloosa civ okay so now what
we're going to do is get rid of this
example and what we're going to do is
we're going to have our number we're
going to have and a can be one equals
two I'm going to have can be two equals
four so I want this number here to equal
either 2 or 4 so how am I going to do
this I'm going to start with if
statement and inside here we're going to
write if so we're saying if number
equals equals remember we're saying is
equal to can be 1 or so remember a
double pipe number equals equals can be
2 so if it equals either 2 or 4 we're
going to echo okay so let's check that
at the moment it's 500 nothing's
displayed so we can write maybe an else
here
Eko not okay so we say not okay
now if this was to equal to that's fine
feels to equal four
that's fine if it was to equal say six
that's not fine because it doesn't equal
the things we've specified now what we
can do is we can change this whole thing
around and I can say not oh sorry I can
say not we use this an exclamation mark
to say not so if this is not true or
this isn't true then it's okay so at the
moment this isn't true
all this isn't true so it is okay oh oh
sorry yeah so it's - so if not if the
number doesn't equal then it's not true
so refresh and all maybe weeds her okay
so yeah obviously these need to be in
brackets because what we're doing is
we're evaluating the statement as a
whole this is a hole here and this is a
hole just here so let's refresh and at
the moment is that okay so it doesn't
equal the number doesn't equal two it
does equal two so it's okay if we to do
four and refresh that's okay as well if
it's anything else other than two and
four with because we've introduced this
knot we're saying hmm oh and at this
point we need to make sure this is and
so
okay so okay I'm confused in my own
logic what we're doing is we're saying
okay if the number is not - and if it's
not for so take a look at this code and
try and sort of understand it but the
logic of it especially speaking into an
English English or you say it to
yourself and you'll understand it a lot
better but that is basically logical
operators