Developing Web Applications

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Developing Web Applications Lecture 7 More
PHP Dr. Ralph Moseley
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• Review
• PHP Basics
• Variables and arrays
• Output
• Sequence, repetition and selection

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• This week
• Forms
• Email
• Functions
• Cookies
• Sessions

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PHP for Forms

• HTML Forms are used to select different kinds of
  user input.
• Make your form using your favourite tool
• Set the form action attribute to
• ltform action"lt?php echo PHP_SELF ?gt"
  method"post"gt - or
• ltform action"script.php" method"post"gt
• Make sure that you name each form field that you
  want to process as these names will be available
  to the processing script as variables
• ltinput type"text" name"inputtext"gt
• inputtext will contain whatever is typed into
  the text field

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PHP for Forms

• When a form is submitted to a PHP script, any
  variables from that form will be automatically
  made available to the script by PHP. If the
  track_vars configuration option is turned on,
  then these variables will be located in the
  associative arrays HTTP_POST_VARS,
  HTTP_GET_VARS, and/or HTTP_POST_FILES,
  according to the source of the variable in
  question.
• Example. Simple form variable
• ltform
  action"foo.php" method"post"gt
• Name ltinput
  type"text" name"username"gtltbrgt
• ltinput
  type"submit"gt
• lt/formgt
• When the above form is submitted, the value from
  the text input will be available in
  HTTP_POST_VARS'username' this is an
  associative array.

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Form Example

• ltHTMLgt
• ltHEADgt
• ltTITLEgtForm example 1lt/TITLEgt
• lt/HEADgt
• ltBODYgt
• lt!-- File form1 --gt
• ltFORM METHOD"POST" ACTIONscript1.php"gt
• Enter a numeric value
• ltBRgtltINPUT TYPE"TEXT" NAME"number"gt
• lt/FORMgt
• lt/BODYgt
• lt/HTMLgt

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Form Example Processing

• ltHTMLgt
• ltHEADgt
• ltTITLEgtForm 1 processinglt/TITLEgt
• lt/HEADgt
• ltBODYgt
• lt! script1.php --gt
• lt?php
• number _POSTnumber
• echo "The number entered was number."
• if (number gt 10)
• echo "ltBRgtThat's a big number."
• ?gt
• lt/BODYgt
• lt/HTMLgt

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PHP Predefined variables

• PHP has a range of predefined variables available
  - for example Apache variables, environment
  variables and PHP-specific variables
• PHP_SELF - the filename of the currently
  executing script
• HTTP_POST_VARS - an associative array of
  variables passed to the current script via the
  HTTP POST method.
• HTTP_GET_VARS - an associative array of
  variables passed to the current script via the
  HTTP GET method.
• HTTP_ENV_VARS - an associative array of
  variables passed to the current script via the
  parent environment.
• SERVER_NAME - the name of the server host under
  which the current script is executing.
• DOCUMENT_ROOT - the document root directory
  under which the current script is executing, as
  defined in the server's configuration file.
• HTTP_REFERER - the address of the page (if any)
  which referred the browser to the current page.
• REMOTE_ADDR - IP address of the client
• REMOTE_HOST - Host name of the client eg browser
• Etc demo phpinfo()

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• Sending an email
• recipient's email address
• to EMAIL
• subject of the message
• re COURSE_TITLE." Submission"
• message from the feedback form
• comments "Hello student, your submission for
  ".COURSE_TITLE." course work has been
  successful\n\n"
• msg comments."\n\nFile file_name\n
  Assignment ass\n Size file_size bytes\n Type
  file_type\n Receipt Code part_code\n\n!Remember
  to keep a copy of this work!\n"
• set the From header
• headers "From ".COURSE_EMAIL
• send the email now...
• mail(to,re,msg, headers)

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Using Custom Functions

• If you have some things that you do in a number
  of different scripts, you might consider putting
  them into custom functions. You could collect
  them into a file called functions.php and include
  them in all your scripts, or you could name them
  individually and include them only as needed.
  For example, you might want to make your own mail
  function which includes some default values. To
  make it flexible, you will want to pass it
  information (arguments) to use in different
  circumstances.

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• You could use the previous email example as a
  function and turn it into one with the header
• my_mail("My sample subject", msg, email)
• You could then include it in all your scripts as
• require (functions.php)

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Functions

• Another example of a function
• function compute_area(height, width)
• return heightwidth
• Function names are not case sensitive
• Return statement terminates function
• Exit() terminates script
• If no return statement NULL is returned

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Default Arguments

• Eg. function gst(amount, rate0.12)
• Return amountrate
• May be called using to override rate
• tax gst(purchase, 0.08)
• Or to use default rate
• tax gst(purchase)

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Cookies and Sessions

• Cookies are useful for storing user info that
  should be retained from one page to the next.
  (Overcome the stateless nature of the web)
• Cookies are written to the clients hard drive.
• Problems
• User can disable cookies in the browser
• Cookies may be viewed by other users
• Can only store 20 cookies max 4KB.
• Some browsers may display incorrectly unless all
  options are set in setcookie()

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Creating a Cookie

• setcookie(name,value,expiration)
• E.g. setcookie(fruit,banana,time()3600) The
  cookies is called fruit and has a value of
  banana it will expire 1 hr from now.
• E.g. setcookie(username,ralph,time()1800)
• Cookie values are sent as part of the HTTP
  headers (transparent to user). No output should
  be sent to the browser (echo etc) until the
  cookie is set else cookie will not be set.

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Accessing a Cookie

• Once created,cookie values are automatically
  available to PHP scripts as a variable having the
  same name as the cookie.
• Eg. echo the current user is username
• PHP associative array HTTP_COOKIE_VARS contain
  the value of every current cookie
• Foreach (HTTP_COOKIE_VARS as name gtvalue)
  echo ltBRgtname gt value

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Deleting a Cookie

• Automatically deleted after expiration time
• Can manually delete by setting negative time
• setcookie(username,,time()-3600)
• Other cookie options
• setcookie(name,value,expire,path,domain,secure)
• pathwhich scripts have access to cookie values?.
  By default, any script in the current server
  directory downward have access. Parent directory
  doesnt.

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Other Cookie Options

• domain by default, a cookie is only available
  to scripts on the current web server. Specify a
  domain name for other servers. NOTE that some
  browsers need at least two dots in the domain
  name (Netscape).
• secure how cookies are sent.
• 1 https (secure connection)
• 0 http (normal connection)
• Eg.setcookie(username,ralph,time()3600,/webr
  oot,http//www.mdx.ac.uk,0)

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Sessions

• Alternative to cookies
• Can use a special cookie to identify the session
• Or pass the session id from one script to the
  next via the URL

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Sessions - Session Variables

• What if user disables cookies? Need to store data
  on the server. This is done in session variables.
• A session variable is a regular global variable
  that, when registered as a session variable,
  keeps its value on all pages that use PHP4
  sessions. To register a session variable, assign
  a value to a variable that is to become a session
  variable and call
• session_register("variable_name").
• On all subsequent pages that uses sessions (by
  calling session_start()), the variable
  variable_name will have the value assigned to it
  before it was registered as a session variable.
  Changes to the variable value will be
  automatically registered in the session and saved
  for further reference

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Session Functions

• session_start -- Initialise session data
• session_destroy -- Destroys all data registered
  to a session
• session_name -- Get and/or set the current
  session name
• session_module_name -- Get and/or set the current
  session module
• session_save_path -- Get and/or set the current
  session save path
• session_id -- Get and/or set the current session
  id
• session_register -- Register one or more
  variables with the current session
• session_unregister -- Unregister a variable from
  the current session
• session_unset -- Free all session variables
• session_is_registered -- Find out if a variable
  is registered in a session
• session_get_cookie_params -- Get the session
  cookie parameters
• session_set_cookie_params -- Set the session
  cookie parameters
• session_decode -- Decodes session data from a
  string
• session_encode -- Encodes the current session
  data as a string
• session_set_save_handler -- Sets user-level
  session storage functions
• session_cache_limiter -- Get and/or set the
  current cache limiter
• session_cache_expire -- Return current cache
  expire
• session_write_close -- Write session data and end
  session

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count.php

• lt?php
• session_start()
• session_register("count")
• count
• msg"You have visited the page count times in
  this session"
• ?gt
• lthtmlgtltheadgtlttitlegtCount visitslt/titlegtlt/headgt
• ltbodygt
• lt?php echo( msg ) ?gt
• lt/bodygtlt/htmlgt

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• Using session variables for authentication in
  conjunction with a database . Create a login-page
  gives the user a userid and password form and
  posts to another PHP page (this example uses
  mysql)  
• lt?php
• session_start()
• if (userid password)
• res mysql_query("SELECT userid FROM users
  WHERE userid'userid' AND password'password'")
  
• if(mysql_num_rows(res) ! 0)
• verified_user userid
• session_register("verified_user")
• Header("Location your_main_page.php")
• ?gt  
• Now, on 'your_main_page.php', you call
  session_start() and then you can check the
  verified_user variable to see if the user has
  been authenticated (and who he is). Other uses
  for session variables, easing database load by
  caching certain values in the session rather than
  reading them from the database on each page
  access.

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Destroying a Session

• lt?php
• // Initialize the session.
• // If you are using session_name("something"),
• // don't forget it now!
• session_start()
• // Unset all of the session variables.
• session_unset()
• // Finally, destroy the session.
• session_destroy()
• ?gt

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Redirection

• Once login data is captured/validated then want
  to go to a new page.
• Header(Location URL)
• header("Location http//ralph-moseley.co.uk/cmt3
  092/lab7.html")
• General technique
• Site start page login page
• Login page validates user and set cookies
• Redirect to new page
• New page uses cookie data to access DB info

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Today

• Forms
• Email
• Functions
• Cookies
• Sessions

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Next Week

• Databases SQL