Beginner PHP Tutorial - 156 - Introduction to GD Video Lecture | PHP for Absolute Beginners: From Novice to PHP Master - Web Development

hello this is Alex from PHP academy' -
all back with another video for the new
Boston now in this short tutorial series
about GED inside PHP we're going to be
talking about what GD is and we're going
to be doing a variety of things with GD
and it's called the GD library
it doesn't actually come with PHP by
default so it's a library that you have
to either install yourself or because
we're using the xampp package as shown
in my previous tutorials how to install
it in windows GD will already come
pre-installed with this and what we do
is we use PHP directly and using this GD
library what we can actually do is we
can generate and we can also modify
graphics so let's take an example and
just speak about an example of what what
how you might find GD useful now you may
have seen websites that allow you to
upload images or or groups of images so
multiple images and you may find that
these are watermarks I know eBay when
you are upload an image it creates a
little watermark in the bottom right
hand corner which sort of you know gives
the image some kind of relation to the
website and this doesn't have to be a
translucent watermark image it can in
fact be some text so you can generate
text with GD you can also watermark
another image over over an image so
there's a variety of things that you can
do with the GD library now another
example maybe you may have seen
registration forms that ask you to enter
some distorted characters or blurred
outs or stretched characters and you'll
obviously know this is for security
purposes now why do we do this we use we
use what
called a capture form or capture image
if you like to allow only human-based
registrations or submission of data
through a form so for example if you
have a form and you want to the data to
be submitted but not submitted in mass
we use something called a capture image
or security image really there is only
human readable or most of the times of
90 plus percent of the time is human
readable so the the distorted text has
to be just has to be read and then input
into another box by a user for the form
to you know or for the user of the
website for the owner of the website to
be satisfied that only humans can
register with this form then obviously
if the incorrect image is entered or the
text from the image is entered then it's
asked to be done again so this prevents
automatic submission of data through
forms now another way to use THD which
is a less commonly used method but a
really interesting good way to use the
GD library and by the way capture forms
or security images if you like and not
always used with GD so there's a variety
of ways you can do this but in my future
tutorials that you may watch you'll see
that we deal with creating our own
capture image using Gd so we're going to
be using GD to Crower own and not allow
a form to be submitted
unless this image is correct so now
another use like I said is less commonly
used but a really really great great way
to go about things is let's say I've
registered on a website and I was to
output my email address so this might be
anything
at anything calm now my email address
let's say we output on my profile page
now if my email address is in text form
so it's in text form that can be picked
up by say a robot for example it's been
programmed to go through websites and
pick up web a pick up email address is
so you'll see some people choose to
write the email address like this sorry
like this or they might do something
like dot there and then at there in
brackets as well vice-versa using
different symbols this is just simply
for security purposes that they do this
however a great way to store an email
address when displaying it in a profile
page to enhance the security of this so
email addresses can't be collected in
max this gives sort of peace of mind to
your users if you store it in an image
forum so what we can do is we can store
this exactly as text so it can be text
but we store it as an image so it can't
be easily picked up by these bots now
I'm not saying it can't be picked up at
all of course it can because the point
of capture forms being distorted is so
it's hard for a bot to read or a
computer program if you like to read but
just by adding this into an image which
is quite a simple process using GD just
gives that added security so it's a lot
more secure to store text as image if
you don't want it to be automatically
picked up by a piece of software that
might be trading through websites trying
to collect specific information so the
GD library like I said is really useful
for mainly these three things that could
you can obviously use it for a variety
of purposes it can it can take images
and change them we can change colors we
can change anything really we're not
going to go into the complexities of
these things because there are loads and
loads and loads of functions used within
GD it's a massive massive library with
lots of functions and lots of ways
to do this so I'm just going to give you
sort of an introduction we're going to
use these three examples we're going to
change some text like this so an email
address into an image we're also going
to be looking at watermarking images as
we upload them or just or just looking a
function to walk watermark images so you
can combine this with an upload script
and we're also going to look at creating
our own capture form so that's basically
the GD library and what its useful if
you are using it if you're having
trouble using it so if the functions
that you're giving that we're going to
look at in other tutorials aren't
working I suggest you go and google for
GD have a look at downloading it and
installing it but otherwise I'd highly
recommend you use it pre-installed on a
package such as xampp like I'm using and
then it'll already already be there for
you installed and it will be available
to use