Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 1 Lecture 6: More PHP Instructor: Dr. Mohammad Anwar Hossain

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 2 Review PHP Basics Variables and arrays Output Sequence, repetition and selection …

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 3 This week: Forms Functions Cookies Sessions

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 4 Forms: how they work We need to know.. 1.How forms work. 2.How to access the data in PHP.

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 5 How forms work Web Server User User requests a particular URL XHTML Page supplied with Form User fills in form and submits. Another URL is requested and the Form data is sent to this page either in URL or as a separate piece of data. XHTML Response

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 6 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 ◦ " method="post"> - or ◦ ; 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 ◦ ◦ $inputtext will contain whatever is typed into the text field

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 7 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 Name: 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.

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 8 Form Example Form example 1 Enter a numeric value:

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 9 Form Example Processing Form 1 processing <?php $number = $_POST[‘number’]; echo "The number entered was: $number."; if ($number > 10) echo " That's a big number."; ?>

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 10 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()

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 11 Sending an #recipient's address $to = $ ; #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_ ; #send the now... mail($to,$re,$msg, $headers);

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 12 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.

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 13 You could use the previous example as a function and turn it into one with the header: my_mail("My sample subject", $msg, $ ); You could then include it in all your scripts as: require (“functions.php”); Using Custom Functions

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 14 Functions Another example of a function: function compute_area($height, $width) { return $height*$width } Function names are not case sensitive Return statement terminates function Exit() terminates script If no return statement NULL is returned

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 15 Default Arguments Eg. function gst($amount, $rate=0.12) { Return $amount*$rate; } May be called using – to override $rate: $tax = gst($purchase, 0.08); Or to use default rate $tax = gst($purchase);

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 16 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 client’s 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()

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 17 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.

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 18 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 $name =>$value) echo “ $name => $value”;

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 19 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 ) path=which scripts have access to cookie values?. By default, any script in the current server directory downward have access. Parent directory doesn’t.

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 20 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”,”Abdallah”,time()+3600,”/webroot”,” ;

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 21 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

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 22 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

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 23 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

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 24 <?php session_start(); session_register("count"); $count++; $msg="You have visited the page $count times in this session"; ?> Count visits count.php

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 25 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): <?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"); ?> 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.

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 26 Destroying a Session <?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(); ?>

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 27 Redirection Once login data is captured/validated then want to go to a new page. Header(“Location: URL”); header("Location: moseley.co.uk/cmt3092/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

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 28 Today: Forms Functions Cookies Sessions

Modified from Moseley ’s sli desWeb Applications Development. Lecture 6 Slide 29 Next Week Databases: SQL