Web forms in PHP Forms Recap  Way of allowing user interaction  Allows users to input data that can then be processed by a program / stored in a back-end database etc  Large amounts of data can pass from the user to the server (parameters can be passed)  Used in areas like e-commerce

Forms – getting the input Use a normal XHTML form to get user input, e.g. … Surname: Address: …

Forms – getting the Input Different form elements can be used to collect input, e.g.   Also radio buttons, checkboxes, select lists, and hidden Action –  Appends data onto end of http request information  Specifies the PHP script stored on the server that we want to send the data to (e.g. processData.php), so that the script can get it and process it Submit  User completes the form and the request for the processing script is sent to the server when the “submit” button is clicked  The script will then run on the server

Forms 1 - requesting the form Client requests the XHTML web form from the server, the server then sends the XHTML web form to the client browser where it is displayed Browser Client (e.g. IE) Response (the text/XHTML of the web form) Web Server Software e.g. Apache / IIS Files in local_html: getDataFrm.html processData.php Web Server Request for getDataFrm.html

Forms 2 - sending data / the response Data entered on the form is sent by the browser (in parameter name-value pairs) along with the request to the server for the PHP script when the form submit button is clicked Browser Client (e.g. IE) Request for processData.php (with parameter name-value pairs e.g. surname – elvin address - SCEIS) Response (text/XHTML) Web Server Software e.g. Apache / IIS Files in local_html: getDataFrm.html processData.php PHP Processor Web Server

Parameter name-value pairs Form data is sent in name-value pairs  e.g. surname-bloggs, game-chess name – the name of the form component specified by the name part of the tag, e.g. … Chess Drafts … value – this is the value entered or selected by the user for the particular form component

GET and POST HTTP governs how web browsers request files from web servers and how servers send files back There are two HTTP methods to pass parameters to the server (to be processed by scripts): GET  GET requests encode form parameters in the URI (in a query string)  i.e. they append data to the URI, e.g. appendExample.php?surname=kasparov, game=chess POST  For posting lots of data to the server  Sends data within the body of an HTTP request  Not sent via the URI, therefore invisible in the browser It is possible to use either with XHTML web forms

Getting and processing data The $_POST and $_GET arrays can be used by a PHP script to access form parameters The keys are the parameter names Example: the PHP code for the processData.php script <?php $surname = $_POST[‘surname’]; $game = $_POST[‘game’]; echo “Surname: $surname "; echo “Game: $game”; ?> Here the parameter values from POST for “surname” and “game” are first copied into variables, and then sent back to the browser in the response for display The response will vary depending on what the user entered You need to use $_POST (or $_GET) for every INPUT field in the web form

Forms: an overview Remember  Forms allow users to input data  Parameter name-value pairs are passed with the request to the server  This data can be processed by the script e.g. get it using $_POST (or $_GET) and store it in variables  The data can be processed in any way that you like, including display back to the browser (using echo) via the response  The data sent to the form can vary, and therefore so can the response The particular response is not saved in a file, it is only seen by the browser that requested the script from the server

Using GET: example Data parameters encoded in the URI (in a Query String) Example: Product 75 Processing PHP script (viewp.php): $prodID = $_GET['productID']; echo "Product Id: $prodID - "; if ($prodID == "55") echo "Blue shirt with polka dots"; if ($prodID == "75") echo "Batman outfit"; Query String

On condition … Conditional statements allow decision making depending on conditions  Allows programs to be dynamic, executing different pieces of code depending on a condition Conditional statements include  if/else  switch

if statement: making decisions Use: evaluate truth of expression (condition). Format of if if (expression) statement else alternative statement if the expression was false elseif format: if (expression 1) statement 1 elseif (expression 2) statement 2 else default statement if both expressions were false What operators are there?  e.g. !=,, >=, <=, ==, &&, AND, ||, OR

Example web site Requests and passes parameters to loginEX.php

Code for loginEx.php … $userN = $_POST[‘username’]; $pass = $_POST[‘password’]; echo "Hello $userN "; if ($pass == “adminpass") { echo " Enter secure Menu area"; } elseif ($pass == "bob") { echo “Successful login Enter site"; } else { echo "Password invalid. Try again "; } …

Some string functions strlen(x)- no of characters in a string strpos(x, “a”)- returns the position, e.g. of a substr(x, start [, length])- copies piece of string substr_replace(x, y, start[, length])- replaces x with y strrev(x)- reverses the string trim(x)- removes white space ltrim(x)- removes white space from start of string rtrim(x)- removes white space from end of string strtolower(x)- to lower case strtoupper(x)- to upper case ucfirst(x)- makes first character upper case ucwords(x)- first character of each word to uppercase

Improving the login system Validating input How could we:  Check if the user name was of the correct length?  Remove white space?  Remove the effect of case?

Code for loginEx2.php … $userN = trim($_POST['username']); if (strlen($userN) !=5) echo "User names must be exactly 5 characters long. Please try again"; else { $pass = strtolower(trim($_POST['password'])); echo "Hello $userN "; if ($pass == "adminpass") { echo " Enter secure Menu area"; } elseif ($pass == "bob") { echo "Successful login Enter site"; } else { echo "Password invalid. Try again "; } } …

Further validation Requests and passes parameters to changePassEx.php How could we: Check that anything had been entered? Check whether the two entries match?

Code for changePassEx.php Another example using control structures and string functions if ((strlen($_POST['newP1']) == 0) && (strlen($_POST['newP2']) == 0)) { echo "You have not entered a new password. Try again"; } elseif ((strlen($_POST['newP1']) == 0) || (strlen($_POST['newP2']) == 0)) { echo "You haven't entered the new password twice"; } elseif (strcmp($_POST['newP1'], $_POST['newP2']) != 0) { echo "The passwords entered are not the same. Please try again. "; } else { echo "Thanks for the new password"; } ?>

switch statement An alternative way of making conditional decisions Unlike with if /elseif, switch evaluates only one expression Used when a single value determines a choice (and also used when if’s start to look confusing) switch (expression) case value1: // code to execute if the expression evaluates to value1 break; case value2: // code to execute if the expression evaluates to value2 break; case value3: // code to execute if the expression evaluates to value3 break; default: // code to execute if none of the cases above are true

switch example: custMenu.php … Some code to display a menu, then Current Special Offers <?php $month = date("n"); switch ($month) { case 2: echo "Love song album deals for Valentines day"; break; case 12: echo "Festive season favourites at half price"; break; default: echo "A general special offer"; } ?> …