LIS651 lecture 0 Gathering and showing data

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LIS651 lecture 0 Gathering and showing data

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Title: LIS651 lecture 0 Gathering and showing data

1
LIS651 lecture 0Gathering and showing data

Thomas Krichel
2007-03-18

2
today

Introduction to the course
Introduction to PHP
HTML forms
Using form data in PHP

3
course resources

Course home page is at http//wotan.liu.edu/home/k
richel/courses/lis651n07s
The course resource page http//wotan.liu.edu/home
/krichel/courses/lis651
The class mailing list https//lists.liu.edu/mailm
an/listinfo/cwp-lis651-krichel
Me.
Send me email. Unless you request privacy, I
answer to the class mailing list.
Skype me at thomaskrichel. Get skype from
skype.com.

4
today

We introduce PHP. Understanding PHP is the most
difficult aspect of the course.
We look at forms filling in to prepare for active
web sites.
We look at how PHP can be used to show the data
that we get from the form.
You should think about what data to get and how
to show it.
Thomas has built a little shop with form and PHP.

5
PHP introduction

PHP is the PHP hypertext processor.
It is a tool that allows for server-side
scripting.
Its predecessor is PHP/IF, Personal Home Page /
Forms Interpreter.
PHP/FI was released by Rasmus Lerdorf in 1995. It
was written in Perl.
PHP/FI version 2. was released in 1997. It was
written in C.
PHP version 5 is the current version.

6
PHP language

PHP is an interpreted language.
You write a series of statements.
Apache hands these statements to the PHP
interpreter.
The interpreter executes these statements one by
one.
When it find an error, it stops running and
signals the error.
Compiled languages are different. They read the
whole program before starting to execute it.

7
Apache and PHP

When a file ends in .php, is not simply sent down
the http connection like other files.
Instead, apache sends the file to the PHP
processor.
It sends to the client whatever the PHP processor
returns.
The PHP processor is a model that lives inside
Apache.

8
good old wotan

Remember we duplicate validated.html when
creating a new new file.
Right-click on validated.html, choose duplicate.
You may be asked to supply your password again.
You erase the contents of the dialog box that
suggests a new file name and put your new file
name in there.
If it contains PHP code, it has to end in .php.

9
first PHP script

Create a file with the name info.php, and the
following contents
lt?php
phpinfo()
?gt
nothing else. This will create a test page that
tells you everything PHP knows about. Look at
some of the variables.

10
comment on info.php

In terms of XML, the lt?php until ?gt part is
called a processing instruction. It is a type of
node that we did not encounter in LIS650.
We can call any part of the file between lt?php
and ?gt a PHP part of the file.
The XML file here contains just the processing
instruction.

11
output of phpinfo()

phpinfo() create a whole web page for you, that
validates against a loose HTML specification.
That page contains a lot of technical detail.
The section we may be interested in is PHP
Variables. It contains variables that we may be
interested in. These are variables that PHP can
understand
from its environment
from the client

12
the magic of PHP

The client never sees the PHP code. It only sees
what the PHP processor has done with the code.
You can write normal HTML code, and you can
switch to writing PHP code pretty much at any
stage.
You can have several PHP parts.
PHP parts can not be nested.
The contents of the PHP part can be called a PHP
script.

13
statements

Like a normal text is split into sentences, a PHP
script is split into statements.
A PHP script contains one or more statements.
Each statements tells the interpreter something.
Each statement is ended by a semicolon.
In our first script there is only one statement.
Each statement is ended with a semicolon!
Think of a statement like a rule in CSS. But
never forget the semicolon!

14
expressions

The stuff before the semicolon is called an
expression.
You can think of an expression as anything anyone
may want to write in a computer program.
So an expression is just a way to talk about
stuff in a program in a more edifying way than
just calling it stuff.

15
functions

phpinfo() is a function.
Functions are one of the most fundamental
concepts in computer programming.
A function is an expression that does something
to something else. The something else is in the
parenthesis. It is called the argument of the
function.
The argument of phpinfo() is empty.

16
second php script hello.php

Normally we write HTML code and then we add PHP
parts.
Take validated.html, copy to hello.php
make the body
ltdivgt
lt?php
print("Hello, world!")
?gt
lt/divgt
Validate the resulting XHTML.

17
comment on hello.php

print() is also a function. print prints its
argument. Here the argument is a string. A string
is a sequence of characters enclosed by single or
double quotes.
For print, the () can be omitted.
You could have written three statements
lt?php
print "ltdivgt"
print "Hello, world!"
print "lt/divgt"
?gt

18
good style

Write each statement on a new line.
Add plenty of comments. There are three styles of
comments in a PHP program
// the rest of the line is a comment
the rest of a line is a comment
/ this is a comment /
Only last style can be used over several lines.
Do you recognize two of the commenting styles?

19
another way to write hello.php

lt?php
greeting"Hello, world!"
print "ltdivgtgreetinglt/divgt"
?gt
Here greeting is a variable. The first statement
assigns it the string value "Hello, world!". The
second statement prints it out.
This example is important because it illustrates
the concept of a variable.
The name of the variable is greeting.

20
Forms

Forms are parts of an HTML document that users
can fill in. They may include buttons,
checkboxes, text areas, file selections.
The thing that users fill in are called the
controls of the form.
Some controls are hidden.
Controls are submitted to PHP in the form of
variables. Each control in the HTML form becomes
a variable in PHP. This is seen later.

21
forms examples

Here is an example in http//wotan.liu.edu/home/kr
ichel/courses/lis651/examples/forms
Elements used in forms use a special attribute
group that I will call the form attributes. I
will discuss them now.

22
form attribute tabindex

Stupid users use the mouse to fill in form. Smart
users use the tab character on the keyboard. It
is much quicker.
if you set the tabindex on a in input, you can
set the order. The value of the attribute is a
number between 0 and 32767. The input with a
lower number will be dealt with before the one
with a higher number.

23
form attribute readonly

If you set readonly"readonly" the control can
only be read but not set. This means
It can receive focus but cannot be modified by
the user.
It is included in tabbing navigation.
It is transmitted to the server for processing.
readonly is not set by default.

24
form attribute disabled

If you set disabled"disabled" the control can
only be read but not set. This means
it can not receive focus and can not be modified
it is excluded in tabbing
it is not transmitted to the server for
processing.
disabled in not set by default.

25
ltformgt

This element encloses a form.
All form elements (discussed now) should be
children of the ltformgt element.
Technically can be more than one ltformgt in the
HTML page.
But it does not make much sense to have several
ltformgts.
ltformgt accepts the core and i18n attributes. And
it has some other attributes. Some of these are
required.

26
the action attribute of ltformgt

It has a required action attribute.
The value of this attribute is the location of a
file that contains the action to execute when the
form is submitted.
In our case, this will be the file name of the
PHP script that deals with the form on wotan.
By default, scripts are executed using return on
the browser while a form element has focus, or a
special submit button.

27
method of ltformgt

ltformgt admits a method attribute. This attribute
determines the http method by which the form is
submitted to the script. There are only two
realistic choices
method"get (default)
method"post"
When the form is submitted the http request line
that follows will have the method GET or POST.
Validation requires lowercase values.

28
method"get"

If you use GET, the form data is transmitted by
appending it to the URL of the script. Google's
Web search does it that way, for example.
There is a standard way to write the data in the
URL knows as Common Gateway Interface, CGI. It is
of no further interest to us.
Advantage you can bookmark the form.
Problem there is a limit of 1024 chars for the
URL, therefore only a limited information can be
transmitted in this way.

29
method"post"

If you use post, the user agent sends the form as
a POST message to the server.
The data is sent in the body of the http request.
Thus it can be as long as you want.
If you use POST you can set the MIME type of the
data with a special attribute enctype

30
more attributes to ltformgt

Here are two more attributes I will list for
completeness
accept-charset says what character sets will be
accepted by the form
accept says what MIME-types can be accepted

31
the form control ltinput/gt

This element creates a control. Usually a form
has several ltinput/gts as well as text that
explains the from.
Note the emptiness of the element.
It admits the core, i18n and the form attributes.
It requires a type attribute and a name
attribute.

32
the type attribute of ltinput/gt

This attribute can only take the following values
text enter text
password enter text, but don't echo on screen
checkbox enter checks on boxes
radio check one select
submit press to submit form
reset reset form
file upload file (can only be done with POST)
hidden hidden form data, not shown
image image map submission, not covered
further
button a button

33
the name attribute of ltinput/gt

This give a name to the control that the users
are setting.
The script that is found by the action attribute
will identify the controls by name. Therefore
every control should have a different name.

34
control name and PHP variable

When the form is passed to the PHP script named
with the action of the the ltformgt the controls
are accessible as PHP variables.
If name is the name of the control, and if the
method is POST, the control is read as the
variable _POST'name'.
If name is the name of the control, and if the
method is GET, the control is read as the
variable _GET'name'.

35
the size attribute of ltinput/gt

It lets you set the size of the input field.
Note that the size of the field may not limit the
input to that size.
When the type is text or password the value
you give to this field is the number of
characters.
Otherwise it is the number of pixels.

36
the maxlength attribute of ltinput/gt

This sets the maximum length on the value.
Note that this is different from the size of the
input field because there is scrolling.
If you don't specify a maximum length there is no
limit.
But it is good security to have a limit.

37
the value attribute of ltinput/gt

This gives the initial value of the ltinput/gt.
The initial value is shown to the user.
value is optional but should be given for the
radio and checkbox type.

38
the checked attributes of ltinput/gt

When the input is of type 'radio', setting the
checked attribute to any value will tell the
browser what button is initially set. Of course
there can only be one of them.
When the input is of type 'checkbox', setting the
checked attribute to any value will make sure it
is checked initially.

39
the src attribute of ltinput/gt

When the input is of type 'image' the src
attribute gives the URL of the image.
This is for input using image maps.

40
example

HTML file greet.html has
ltform action"greet.php" method"get"gtltpgt
your last name ltinput type"text"
name"lastname"/gtlt/pgtlt/formgt
PHP file greet.php has
lt?php
print "Hello "
print _GET'lastname'
?gt
in addition to the usual HTML stuff.

41
the push button ltbuttongt

This makes a button for decoration.
It takes a type attribute that can be either be
'button', 'submit' or 'reset'.
It has takes a name attribute for the name of
the control that it sets.
It takes a value attribute attribute to set a
value.
It also takes the core and i18n attributes.
And it can have character contents!
I am not sure what it is good for.

42
creating menus

This is done with ltselectgt element.
Each ltselectgt element can have a number of
ltoptiongt elements that contain the options that
the user can choose from.
ltselectgt also takes the core and i18n attributes,
and some others that we see now.

43
attributes to ltselectgt

name has the name of the control that is set
multiple"1" allows and multiple"0" (default)
disallow multiple selections. However, I don't
know how they are being transmitted. Therefore I
suggest you don't use this option.
size sets how many rows of the selection should
be displayed at any one time.

44
selectable choice ltoptiongt

Within a ltselectgt there are a series of ltoptiongt
elements that contain the selections.
ltoptiongt takes the core, i18n and form
attributes. Example
ltselect name"brewery"gt
ltoptiongtBruchlt/optiongt
ltoptiongtKarlsberglt/optiongt
lt/selectgt

45
value attribute to ltoptiongt

value can be used to set the value of the
control when the value set is different than the
contents string of the ltoption/gt element.
Example
ltoption value"nyc"gtNew York Citylt/optiongt

46
other attribute to ltoptiongt

label can be set to label the option. if it is
set, the user agent should use label rather than
the content of the ltoptiongt element. At least
this is what the spec says. Firefox does not seem
to agree. See forms/options.html for a test
example.
selected can be used to select an option.

47
ltoptgroupgt

This element has ltoptiongt elements as its
children.
It takes the same attributes as ltoptiongt.
It is used to create hierarchical options. This
is mainly a time and space-saving device in the
presence of many options. Say
ltoptgroup label"dark"gt
ltoption value"b6"gtBaltika 6lt/optiongt
ltoption value"gu"gtGuinness"/gtlt/optiongt
lt/optgroupgt

48
the lttextarea/gt element

This creates a text area where you can put a
large chunk of text.
It takes some attributes
name sets the name of the control that is set.
cols sets the number of columns in the text
area.
rows sets the number of rows in the text area.
lttextarea/gt also admits the i18n, core and form
attributes.

49
ltlabelgt

This is a way to add labels for inputs.
Normally, the input label should be taken from
the label attribute of the input.
ltlabelgt can be used if the other method can not
be.
It accepts a for attribute to give the input for
which it is the label is for. Example
ltinput name"sex"/gtltlabel for"sex"gtyour
sexlt/labelgt

50
summary

Forms deliver data to the server. The server can
then process the data and deliver a response.
Active effects can also be done client-side. This
is done using the ltscriptgt element that mostly
uses a language called javascript.

51
homework

You create a file test_form.html in your space on
wotan that has a form. Whatever form you like.
You write a PHP script that displays the contents
of the form, and give it as the action attribute
to the form.
I will look for the form if you dont do well on
the next quiz and give you a better grade (a
so-called form-aided grade), if it works.

52
for help with the PHP

Here is one that I made earlier. In the course
resource site find examples/forms/list_get.php.htm
l
Dont be too worried about the contents of this
file.
You can make this your PHP file that is called by
the form if you use GET. Otherwise, replace the
GET in the file by POST.
Create a cut-and-paste copy of it in a file
ending with .php.

53
complete example shop

We build a form, that allows people to buy things
in a shop.
The result of the form is the itemized bill,
including totals with sales tax!
When you are done, you can go home or to the pub.
I advice you not to go to either home or pub
until you are done.

54
master example greet.php

lt?php
if(_GET'submitted')
name_GET'name'
print "ltdivgtHello name!lt/divgt\n"
else
print "ltform action\"greet.php\"
method\"get\"gt\n"
print "ltdivgtltinput type\"hidden\"
name\"submitted\" value\"1\" /gtlt/divgt\n"
print "ltpgtYour name ltinput type\"text\""
print " name\"name\" value\"name\" /gt"
print "lt/pgtlt/formgt\n"
?gt