Advance Database Management Systems Lab no. 5 PHP Web Pages
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Advance Database Management Systems Lab no. 5
PHP Web Pages
IntroductionSo far we have considered static web pages.We used PHP scripts to write simple programs
with (built-in) capability to perform computationNow, we’d like to build smarter pages which
Respond to user’s actionsRetrieve dynamic informationSupport conditional behavior
Problem: Handling user input
We still don’t have a way to get input from the user.
Note:PHP does not have its web controls as ASP has.
Getting User InputThere can be two ways of getting Input
data from user
URL Paremeters and $_GET arrayWeb Forms (HTML CONTROLS)
URL ParametersPHP has the capability to pull parameters
out of the URL query string Parameters can be passed as text after the
file name, e.g., http://localhost/test.php? name=john & age=2
Parameter names and values can be accessed as variables using specialarray named $_GET
URL Parameters Example
Browser retrieves the URL:http://local host/test.php?name=john
&age=2
in test.php
<?phpecho $_GET[“name”]; // displays johnecho $_GET[“age”]; // displays 2?>
Web Forms (HTML Controls)We need a more elegant way of passing
parameters to PHP pages HTML forms can be used to accept input
from users which contain a set of input tagsText boxes, checkboxes, etc.
Form pages can submit data to a PHP pagePass input values in query string
Creating web formsForm tag controls what is done with data
<form action="results.php" method="get” name="hello">
<!-- form input controls go here -->
</form>
action: Page to submit results tomethod: How to submit data, name: Used to refer to the form
Form ActionsThe form’s ACTION is the name of the PHP
script (points to PHP page)When the user submits the form
the web server executes the PHP script in results.php file
Form submission methodsHTTP supports two methods for submitting form
data GET
Parameters are passed in URL stringParameters visible to user in browser windowEasy to debug
POSTParameters included in body of HTTP requestNot visible to userCan handle larger data items
$_GET Function
The built-in $_GET function is used to collect values from a form sent with method="get".
Information sent from a form with the GET method is visible to everyone (it will be displayed in the browser's address bar) and has limits on the amount of information to send (max. 100 characters).
When to use method="get"?When using method="get" in HTML forms, all
variable names and values are displayed in the URL.
Note: This method should not be used when sending passwords or other sensitive information!
However, because the variables are displayed in the URL, it is possible to bookmark the page. This can be useful in some cases.
Note: The get method is not suitable for large variable values; the value cannot exceed 100 characters.
Form inputsAllow users to input data Generally have a name and a value Map to parameters when form is posted
Text box Textarea (larger text box)Checkbox Radio buttonMenuSubmit button
HTML Controls RECAP
Text input/Text Box
One-line text input<input type="text" name="message“
value="Welcome" size="40“ maxlength="25“ />
name: input name value: default value size: length (in characters) maxlength: Maximum number of characters to
accept
Text areaLarger, multiline text box<textarea name=“box” cols=“25”
rows=“6”> Default text goes inside tags </textarea>
Name: input name Cols: width (in characters) Rows: number of rows
CheckboxCheckbox, allows for boolean choices<input type=“checkbox” name=“test“
value=”true" checked=“checked” />
Name: input name Value: value if checked (name=value) Checked: if included, box is checked by
default
Select (pulldown or menu)
Allows user to choose item from a dropdown menu<select name=”beverage"><option value=”coffee">I prefer coffee</option><option value=”tea">I prefer tea</option></select> Will submit variable “beverage” withvalue “coffee” or “tea”
Radio button Presents multiple options, user chooses one<input type="radio" name=”fruit" value=”apple“
checked=“checked” /><input type="radio" name=”fruit" value=”papaya” /><input type="radio" name=”fruit" value=”mango” /> Each item in a group has same name, different value Only one button can be checked by default Value of parameter fruit will be apple, papaya,mango
Hidden fieldSometimes we want to pass data to forms
without user’s input User’s password, current time<input type=“hidden” name=“key”
value=“hello” /> Won’t be shown to user Will pass parameter “key=hello” to form
Submit buttonWhen clicked, submits form data to target<input type=”submit" value=”Submit
form” /> Value: Label of submit button
Labeling form elementsThe most common way to add labels is simply to
place text beside the form input Add me to mailing list: <input type=”checkbox"
name=”addtolist"
value=”true" checked=“checked” />
<br/>
Save password: <input type=”checkbox" name=”savepw” value=”true"
checked=“checked” />
Other PHP server variables
$_POST Like $_GET, but for POST requests
$_REQUEST Searches both GET and POST for parameters
$_SERVER Stores additional information from server
User’s IP address, host URL, etc
$_POSTThe built-in $_POST function is used to collect
values from a form sent with method="post".Information sent from a form with the POST
method is invisible to others and has no limits on the amount of information to send.
Note: However, there is an 8 Mb max size for the POST method, by default (can be changed by setting the post_max_size in the php.ini file).
<form action="welcome.php" method="post">Name: <input type="text" name="fname" />Age: <input type="text" name="age" /><input type="submit" /></form>
When the user clicks the "Submit" URL will change to welcome.php.
in "welcome.php" file,we can now use the $_POST function to collect form data (the names of the form fields will automatically be the keys in the $_POST array): Welcome <?php echo $_POST["fname"]; ?>!
<br />You are <?php echo $_POST["age"]; ?> years old.
$_POST Example
Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.
When to use method “POST”?
$_REQUEST The PHP built-in $_REQUEST function
contains the contents of both $_GET, $_POST, and $_COOKIE.
The $_REQUEST function can be used to collect form data sent with both the GET and POST methods.
ExampleWelcome <?php echo $_REQUEST["fname"]; ?>!<br />You are <?php echo $_REQUEST["age"]; ?> years old.
$_REQUEST
$_SERVERWhen the variable has been assigned from
the server
$_SERVER
Example
<html><head><title>Test page</title></head><body><!-- content goes here --><!-- these are HTML comments --><h1>Form demo</h1><form action="results.php" method="get"name="hello">Enter message:<input type="text" name="message"value="Hi“ /><input type="submit" value="Go!“ /></form></body></html>
Accessing form data//results.php<?php$user = $_GET[“username”];echo “You entered “ . $user;?>
Form validation When we process forms, we can’t be sure that the user included correct information May have left fields blank May have put in improper information Never Trust User Input! We may want to validate the form input before using it PHP provides a number of functions to help us validate form input
isset() is variable null? is_numeric() is variable a numeric type? is_string() is variable a string?
Validation example
<?php// multiply a number by two// get parameter “num” from url string$num = $_GET[“num”];// is $num a number? if not, throw an errorif (!is_numeric($num)) {echo “Error!”;}else {echo $num*2;}?>
Including librariesPlace PHP file in same directory or
subdirectory Simpler than Java, no packages or
namespaces Essentially pastes included code into file
PHP Include File Server Side Includes (SSI)
You can insert the content of one PHP file into another PHP file before the server executes it using two types of functions.
include() generates a warning in case errors in included
file, but the script will continue execution require()
generates a fatal error, and the script will stop These two functions are used to create
functions, headers, footers, or elements that will be reused on multiple pages.
Server side includes saves a lot of work. This means that you can create a standard header, footer, or menu file for all your web pages. When the header needs to be updated, you can only update the include file, or when you add a new page to your site, you can simply change the menu file (instead of updating the links on all your web pages).
Include examplein math.php:<?php
function mult($n1,$n2) { return $n1*$n2; }
?>
in index.php:<?php
include(“math.php”);echo mult(15,5);
?>
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