LIS651 lecture 0 Gathering and showing data

1
LIS651 lecture 0Gathering and showing data

• Thomas Krichel
• 2006-03-11

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course resources

• Course home page is at http//wotan.liu.edu/home/k
  richel/courses/lis651n06s
• 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.

3
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.

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PHP introduction

• PHP is the PHP hypertext processor.
• It is a tool that allows for server-side
  scripting.
• It 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.

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Apache and PHP

• When a file ends in .php, is not simply sent down
  the http connection like other files.
• Instead, apache reads the file. If it finds PHP
  parts in the file, it sends them to the PHP
  processor.
• This processor is a model that lives inside
  Apache.

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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.

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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.

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comment on info.php

• If a file has the ending .php, Apache may not
  show the entire file to the client as is.
• Instead Apache reads the file. When it finds
  lt?php, Apache calls another program, the PHP
  processor. Then the PHP processor interprets the
  content of the file from that point onwards,
  until it encounters ?gt.
• We can call any part of the file between lt?php
  and ?gt a PHP part of the file.
• Parts of the file that are not in a PHP part are
  sent to the clients as such.

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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

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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.

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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!

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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.

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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.
• phpinfo() is a function. Its argument is empty.

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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.

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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

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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?

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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.

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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.

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forms examples

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

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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.

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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.

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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.

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ltformgt

• This element encloses a form.
• All form elements (discussed now) should be
  children of the ltformgt element.
• There can be more than one form 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.

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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.

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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"
• method"post"
• When the form is submitted the http request line
  that follows will have the method GET or POST.
• Validation requires lowercase values.

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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.

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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

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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

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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.

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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

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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.

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control name and PHP variable

• When the form is passed to the PHP script named
  with the action attribute of the the form, 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'.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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

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label 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.

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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"gtGuiness"/gtlt/optiongt
• lt/optgroupgt

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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.

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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

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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.

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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.

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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.

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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.

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saar_bier.html, part 1

• ltform action"saar_bier.php" method"post"gt
• lttablegt
• lttrgtlttd valign"top" rowspan"2"gtlta
  href"http//www.grosswald.de"gt
• Grosswald Brauereilt/agt (since 1860)lt/tdgt
• lttdgtPilsenerlt/tdgtlttdgt
• ltinput type"text" name"gw_pils" size"2"/gt
• lt/tdgt
  lttdgt_at_1.56euro
• ltinput type"hidden" name"p_gw_pils"
  value"1.56"/gt

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saar_bier.html, part 2

• lt/tdgtlt/trgtlttrgtlttdgtExportlt/tdgtlttdgt
• ltinput type"text" name"gw_expo" size"2"/gt
• lt/tdgt
  lttdgt_at_1.34euro
• ltinput type"hidden" name"p_gw_expo"
  value"1.34"/gt
• lt/tdgtlt/trgt
• lttrgtlttd valign"top"gtBrauerei Bruch (since
  1702)lt/tdgt
• lttdgtLandbierlt/tdgtlttdgt
• ltinput name"bruch_land" type"text" size"2"/gt
• lt/tdgt
  lttdgt_at_1.22euro
• ltinput type"hidden" name"p_bruch_land"
  value"1.22"/gt

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saar_bier.html, part 3

• lt/tdgtlt/trgt
• lt/tablegt
• ltdivgt
• ltinput type"hidden" name"euro_rate"
  value"1.22"/gt
• ltinput type"submit" value"I order!"/gt
• lt/divgt
• lt/formgt

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saar_bier.php, part 1

• lt?php
• gross_pils_POST'gw_pils'
• p_gross_pils_POST'p_gw_pils'
• t_gross_pilsp_gross_pilsgross_pils
• gross_expo_POST'gw_expo'
• p_gross_expo_POST'p_gw_expo'
• t_gross_expop_gross_expogross_expo
• bruch_land_POST'bruch_land'
• p_bruch_land_POST'p_bruch_land'
• t_bruch_landp_bruch_landbruch_land

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saar_bier.php, part 2

• // add up the grand total in euros
• // note how this statement stretches several
  lines
• total_eurot_gross_pils
• t_gross_expo
• t_bruch_land
• // get the euro rate from the form
• euro_rate_POST'euro_rate'
• // calculate the total dollars
• total_dollartotal_euroeuro_rate

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saar_bier.php, part 3

• print "ltdivgt You ordered ltulgt"
• print "ltligtgross_pils bottles of Grosswald Pils,
• cost t_gross_pilslt/ligt"
• print "ltligtgross_expo bottles of Grosswald
  Export,
• cost t_gross_expolt/ligt"
• print "ltligtbruch_land bottles of Bruch Landbock,
• cost t_bruch_landlt/ligtlt/ulgt"
• print "Your bill is total_dollar US
  dollars.ltbr/gt"
• print "We ship when we get your check!ltbr/gt"
• print "Prosit!lt/divgt"
• ?gt lt!-- normal HTML goes on hereafter ... --gt

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