Final Exam. IT 3203 Introduction to Web Development. Rescheduling Final Exams. PHP Arrays. Arrays as Hashes. Looping over Arrays

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1 IT 3203 Introduction to Web Development Introduction to PHP II April 5 Notice: This session is being recorded. Copyright 2007 by Bob Brown Final Exam The Registrar has released the final exam schedule. You can find your complete schedule in BANNER. The final exam for this course is: May 3, 2:00 3:50 PM Note the change in time from the regular course meeting time. The on-line syllabus has been updated. Rescheduling Final Exams If a student is scheduled to take three or more final exams on the same day, the student may request that exams be rescheduled. The course with the highest catalog number will reschedule the exam. Full details are here: (scroll to the bottom) PHP Arrays There is only one kind of array Subscripts may be either integers or strings $people=array('bob','carol','ted', 'Alice); // $people[0] is 'Bob' $people[]='george'; // $people[4] is now 'George' Looping over Arrays The foreach loop: foreach ($people as $x) { echo $x,' '; // Prints: Bob Carol Ted Alice George Arrays can be associative: Arrays as Hashes $cast=array('carol'=>'natalie Wood', 'Bob'=>'Robert Culp', 'Ted'=>'Elliott Gould'); $cast['alice']='dyan Cannon'; echo "Carol is played by $cast['carol']<br />"; 1

2 Contents of a Hash The foreach loop works on associative arrays foreach ($cast as $role => $actor){ echo "$role is played by $actor"; echo '<br />'; Retrieving Array Elements in Order Arrays have an internal pointer you can manipulate: current, next, prev, reset $stooges=array ('Curly', 'Larry', 'Moe') ; $stooge=current ($stooges) ; echo $stooge ; Curly $stooge=next ($stooges) ; echo $stooge Larry Key/Value Pairs each returns key/value pairs in array order $cast=array ('Carol' => 'Natalie Wood', 'Bob' => 'Robert Culp', 'Ted' => 'Elliott Gould'); while ($actors=each ($cast)) { $role=$actors['key']; $actor=$actors['value'] The internal array cursor is not reset. Arrays as Stacks array_push and array_pop $stooges=array ('Curly', 'Larry', 'Moe') ; $len=array_push ($stooges, 'Shemp') ; // $stooges is Curly, Larry, Moe, Shemp // $len is 4 $result=array_pop ($stooges); // $result is Shemp (or NULL) // $stooges is Curly, Larry, Moe Deleting Deleting an array element unset($list[2]); Note typo in some textbooks. Deleting an entire array String to Array The explode function splits a string on a delimiter and places the result in an array $str="april in Paris is expensive."; $words=explode(' ',$str); unset($list); 2

3 Array to String The implode function builds a string from the elements of an array. $str=implode(' ',$people); // $str is "Bob Carol Ted Alice George" Sorting The sort function sorts an array strings come first then numbers subscripts are reordered sort($people); // Now Alice, Bob, Carol, George, Ted Sorting hashes: asort Reverse order: rsort and arsort Functions Definition function sq($x) { return $x*$x; Parameters are passed by value For call-by-reference, place & before either the formal or actual parameter Scope is local by default. (Good.) global $i; Call by Reference/Value function add_one($first, $second, &$third) { $first++; $second++; $third++; $a=3; $b=3; $c=3; add_one($a, &$b, $c); Lifetime of Variables Local variables are created each time a function is called and destroyed when the function returns. Static variables are created when a function is first called and survive until the script terminates. function do_it($param) { static $count=0; $count++; echo "We've been called $count times."; Pattern Matching You can use Perl or Posix style regular expressions if (preg_match("/^php/",$str)) echo 'Begins with PHP'; else echo 'Doesn\'t!'; An optional third parameter is an array for storing matching strings. 3

4 PHP and Forms PHP is outstanding for processing forms data. If register globals is set, form control names are automatically assigned PHP variable names. <input type="text" name="address"> In your form echo $address; In PHP But, register globals has an important security flaw. <input type= "hidden" name="loggedin" value= "true"> Access to Form Variables Here s the right way: or $address=$_get['address']; $address=$_post['address']; Can t use $_GET or $_POST directly in an echo; extract to scalar variables instead. HTML Names and PHP Periods are legal in HTML names PHP converts periods to underscores Solution: avoid periods in form element names. PHP and <select> The form below will return snacks=coke if CocaCola is selected. <select name="snacks"> <option value="coke">cocacola</option>... </select> $snack = $_POST["snacks"]; Other Predefined Global Variables $_COOKIE Name value pairs in any cookies $user=$_cookie['user']; $_SERVER Much information about the Web server itself, and this transaction, eg e.g. $req=$_server['request_method'] Relationship of HTML and PHP HTML <form method = "post" > <input type="text" name="address" /> 1100 S. Marietta Parkway $address=$_post['address']; 4

5 Creating Forms with PHP You can obtain values from a database. Repetitious entries are easy. <form action="..."> <select name="favorite"> <?php foreach ($cast as $role=>$actor) { echo "<option value=\"$role\">", "$actor</option>\n";?> Creating Forms with PHP The code on the previous slide produces one line like the following for each entry in $cast: <option value="alice">dyan Cannon</option>\n"; Creating Cookies The setcookie function creates cookies Parameters: name, value, expiration time setcookie('user',$user,time()+600); This comes back as: $_COOKIE['user'] Cookies are part of the header; you must do this before anything is sent. Even a blank line will mess things up. Approaches to Session Handling Save state in a database Use one of these techniques to save database ID cookies append to URL../myprog.php?dbid=1234 hidden variable in form Consider encryption. Remember, browser users can reject cookies. Session ID in a Hidden Variable <input type="hidden" name="dbid" value="1234"> Not really hidden; visible in view source Think about session hijacking... Make your session ID opaque Consider encryption. About PHP Sessions PHP sessions use cookies if available; Otherwise, session information is appended to the URL, like forms with GET. You can specify session.use_cookies_only; Sessions then will not work if cookies are off. With a database, you can save session variables on the server; only the session ID needs to be sent. 5

6 An Approach to PHP Programming Use two PHP programs: Program A paints a form, has space for error messages Program B processes the form If all is well, B produces a success page, or goes to the next process step If error B, sets messages, calls A with a PHP include A Trivial Input Program <html> <head> <title>process the Frammis Code</title> </head> <body> <h1>this Form Collects Frammis Codes</h1> <form action="frammisb.php" method="post"> <?php if (isset($error)) // Only defined if called from B echo "$error<br />"; else echo '<br />';?> <p>enter Frammis Code: <input type="text" name="frammis"> </p> <input type="submit" value="submit"> </body> </html> The Input Program on the Screen The Processing Program <?php if (isset($_post['frammis'])$frammis=$_post['frammis']; if (!isset($frammis)) $error="<b>frammis code may not be blank!</b>"; if ($error) { include('frammisa.php'); exit;?> <html> <head> <title>success!</title> </head> <body> <h1>frammis Code Processed</h1> <p> <?php echo "Your Frammis code: $frammis was processed successfully!";?></p><p> <!-- Provide a way out! --> <a href="home.html">home</a></p> </body> </html> Success! Error 6

7 Programming Notes Validate as much as possible before sending error messages. Decorate the error messages to make them visible. Be friendly, humane. On busy screens, use a general error message and something like a red asterisk beside error fields. Always provide an escape. Look up Professor James Hendler 7

8 Questions 8