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Lecture 8

Lecture 8. Sessions 27/2/12. ? Operator. Similar to the if statement but returns a value derived from one of two expressions by a colon. Syntax: (expression) ? Returned_if_expression_is_true: returned_if_expression_is_false;. Example. <html> <head> <title>Example</title> </head>

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Lecture 8

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  1. Lecture 8 Sessions 27/2/12

  2. ? Operator • Similar to the if statement but returns a value derived from one of two expressions by a colon. • Syntax: (expression) ? Returned_if_expression_is_true: returned_if_expression_is_false;

  3. Example <html> <head> <title>Example</title> </head> <body> <?php $mood="sad"; $text=($mood=="happy")?"I’m in a good mood":"Not happy but $mood"; print "$text"; ?> </body> </html>

  4. Date • The PHP date() function is used to format a time or a date • The PHP date() function formats a timestamp to a more readable date and time.

  5. Example <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta content="text/html; charset=windows-1252" http-equiv="Content-Type" /> <title>Untitled 1</title> </head> <body> <?php echo("Result with date():<br>"); //The ISO-8601 numeric representation of a day (1 for Monday through 7 for Sunday) echo(date("l") . "<br>"); //d - date in numbers //S - suffix for date //F - A full textual representation of a month (January through December) //Y - A four digit representation of a year //h - 12-hour format of an hour (01 to 12) //i - Minutes with leading zeros (00 to 59) //s - Seconds, with leading zeros (00 to 59) //A - Uppercase AM or PM echo(date("l dS \of F Y h:i:s A") . "<br>"); ?> </body> </html>

  6. Server Side Includes • You can insert the content of a file into a PHP file before the server executes it, with the include() or require() function • The two functions are identical in every way, except how they handle errors • The include() function generates a warning (but the script will continue execution) while the require() function generates a fatal error (and the script execution will stop after the error)

  7. Include Files • These two functions are used to create functions, headers, footers, or elements that can be reused on multiple pages • This can save the developer a considerable amount of time • This means that you can create a standard header or menu file that you want all your web pages to include

  8. include() The include() function takes all the text in a specified file and copies it into the file that uses the include function.

  9. <?php include("inc2.php"); ?> <html> <body> <h1>Welcome to my home page</h1><p>Some text</p> </body> </html>

  10. Include File – incnew.php <html> <body> <a href="http://www.yahoo.com">Yahoo</a> | <a href="http://www.hotmail.com">Hotmail</a> | <a href="http://www.ireland.com">ireland</a> </body> </html>

  11. The require() Function • Identical to include(), they only handle errors differently • The include() function generates a warning (but the script will continue execution) while the require() function generates a fatal error (and the script execution will stop after the error)

  12. Sessions • When you are working with an application, you open it, do some changes and then you close it • The computer knows who you are. It knows when you start the application and when you end • But on the internet there is one problem: the web server does not know who you are and what you do because the HTTP address doesn't maintain state

  13. Sessions • A PHP session allows you to store user information on the server for later use (i.e. username, shopping items, etc) • Session information is temporary and will be deleted after the user has left the website • If you need a permanent storage you may want to store the data in a database • A PHP session variable is used to store information about, or change settings for a user session • Session variables hold information about one single user, and are available to all pages in one application

  14. Session Variables • Sessions work by creating a unique id (UID) for each visitor and store variables based on this UID • The UID is either stored in a cookie or is propagated in the URL

  15. Starting a session <?php session_start();?> <html> <body> </body> </html> This code register the user's session with the server, allow you to start saving user information, and assign a UID for that user's session.

  16. Storing a session variable <?php session_start(); // store session data $_SESSION['newuser']=1; ?> <html> <body> <?php //retrieve session data echo "New user has viewed the page=". $_SESSION['newuser']; ?> </body> </html>

  17. Session Example <?php session_start(); if(isset($_SESSION['pageview'])) $_SESSION['pageview']=$_SESSION['pageview']+1; else $_SESSION['pageview']=1; echo "Number of times page viewed by user=". $_SESSION['pageview']; ?>

  18. Killing a Session • If you wish to delete some session data use the unset() or the session_destroy() function • The unset() function is used to free the specified session variable • session_destroy() will reset your session and you will lose all your stored session data

  19. End a Session <?php session_start(); if(isset($_SESSION['pageview'])) $_SESSION['pageview']=$_SESSION['pageview']+1; else $_SESSION['pageview']=1; echo "Number of times page viewed by user=". $_SESSION['pageview']; unset($_SESSION['pageview']); ?> <?php session_destroy(); ?>

  20. More Sessions • A PHP session is started either explicitly by session_start(), or implicitly by registering a variable for the session, using session_register() • Call session_start() on top of the page, so that session variables are available to your script, and register variables to the session later in the script

  21. More Sessions • if you registered your session variables with session_register() in the head of the script and left out the session_start() call • session_register() calls session_start() internally, if the session isn't started yet • When you start a session, the following happens: • PHP checks whether a valid session ID exists • If there is no session ID, PHP creates a new ID • If a valid ID exists, the frozen variables of that session are reactivated and introduced back to the global namespace

  22. Sessions • Note that this function takes the name of a variable as argument, not the variable itself • You can use session_unregister() to remove variables from the session, for example, when the user removes a product item from the shopping cart

  23. <?php session_start(); print("<html><pre>"); $_SESSION["MyLogin"] = "Ciara"; print("A value saved in the session named as Login.\n"); $_SESSION["MyColor"] = "Blue"; print("A value saved in the session named as Colour.\n"); print("Click <a href=newsess2.php>Next Page</a>"." to retrieve the values.\n"); print("</pre></html>\n"); ?> <html> <head> <title>New Page 1</title> </head> <body> </body> </html>

  24. <?php session_start(); print("<html><pre>"); $myLogin = $_SESSION["MyLogin"]; print("Value of MyLogin has been retrieved: ".$myLogin."\n"); $myColor = $_SESSION["MyColor"]; print("Value of MyColor has been retrieved: ".$myColor."\n"); print("</pre></html>\n"); ?> <html> <head> <title>New Page 1</title> </head> <body> </body> </html>

  25. PHP Cookies • Cookie is often used to identify a user • A cookie is a small file that the server embeds on the user's computer • Each time the same computer requests a page with a browser, it will send the cookie too • With PHP, you can both create and retrieve cookie values

  26. How to create a cookie? • The setcookie() function is used to set a cookie • The setcookie() function must appear BEFORE the <html> tag • Syntax • setcookie(name, value, expire, path, domain);

  27. setcookie(name, value, expire, path, domain); Name = $_COOKIE[“cookiename”] Value = value of cookie Expire= expiry time of cookie Path=the path on the server on which the cookie will be available e.g. test/exam/ Domain = the domain on which it will be available e.g. example.com Secure= whether or not it should use a secure HTTP connection

  28. How to retrieve a Cookie value? The PHP $_COOKIE variable is used to retrieve a cookie value Use the isset() function to find out if a cookie has been

  29. Cookie Example <?php setcookie("user","NoraBatty",time()+3600); setcookie("age", 6 ,time()+3600); setcookie("country","Ireland",time()+3600); ?> <html> <head> <title>Set Cookie and Read Cookie on same page</title> </head> <body> <br> <?php echo $_COOKIE["user"]; echo "<br>"; echo $_COOKIE["age"]; echo "<br>"; echo $_COOKIE["country"]; ?> </body> </html>

  30. How to delete a cookie? • When deleting a cookie you should assure that the expiration date is in the past • Example <?php // set the expiration date to one hour agosetcookie("user", "", time()-3600); ?>

  31. If your browser does not support cookies? • If your application deals with browsers that do not support cookies, you will have to use other methods to pass information from one page to another in your application • One method is to pass the data through forms

  32. Cookie Example <?php setcookie("veg","carrot", time()+3600); ?> <html> <head> <title>New Cookie</title> </head> <body> <?php if (isset($_COOKIE["veg"])) print $_COOKIE["veg"]; else print "<p>Hello. This may be your first visit</p>"; ?> </body> </html>

  33. Cookies • In order to see all of the cookies set: print_r($_COOKIE); • This will show all cookies currently contained in the cookie array

  34. More Cookies <?php setcookie("LoginName","Ciara"); setcookie("PreferredColor","Blue"); print("2 cookies were delivered.\n"); ?> <html> <head> <title>New Page 1</title> </head> <body> <a href="getcook.php">Move to get cookie page</a> </body> </html>

  35. <html> <head> <title>Cookie</title> </head> <body> <?php if (isset($_COOKIE["LoginName"])) { $loginName = $_COOKIE["LoginName"]; print("Received a cookie named as LoginName: ".$loginName."\n<br>"); } else { print("Did not received any cookie named as LoginName.\n<br>"); } print("All cookies received:\n<br>"); foreach ($_COOKIE as $name => $value) { print " $name = $value\n<br>"; } ?> </body> </html>

  36. <?php $Month = 2592000 + time(); //this adds 30 days to the current time setcookie("AboutVisit", date("F jS - g:i a"), $Month); ?> <html> <head> <title>Cookie Tracking</title> </head> <body> <?php if(isset($_COOKIE["AboutVisit"])) { $last = $_COOKIE["AboutVisit"]; echo "Welcome back! <br> You last visited on ". $last; } else { echo "Welcome to our site!"; } ?> </body> </html>

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