Server-Side Scripting with PHP
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CSC 2720
Building Web Applications
Server-side Scripting with PHP
Overview of Server-Side Scripting
Web Client
HTTP
Request
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HTTP
Response
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Web
Server
Static Content
(HTML, Images, etc.)
Runtime environments
for server side scripts
(PHP, Perl, JSP, etc.)
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PHP
Scripts
Perl
Scripts
JSP
Scripts
Overview of Server-Side Scripting
1. Web client sends a HTTP request to a server
A HTTP request consists of
A request method: GET, POST, HEAD, PUT, etc. (GET and
POST are the two most common used methods)
A URI that identifies the requested resource
Header fields
A body (which can be empty)
2. Web server determines how to retrieve the requested
resource.
In the web server configuration file, one can specify how a particular
kind of resources is to be handled. For examples,
Files with .php extension To be handled by the PHP module
Files with .html, .jpg, .gif extensions To be retrieve directly
Files in folder /xxx/yyy/ To be treated as CGI scripts
…
Overview of Server-Side Scripting
3. Runtime environment
A runtime environment typically has the following
capabilities
Interpreting/executing the server-side scripts
Maintaining sessions
Parsing incoming HTTP request and generating outgoing HTTP
response
Caching generated output, frequently-used scripts, etc.
Different scripting languages may require different runtime
environments
4. The requested script is processed by the corresponding
runtime environment and the generated output is placed in
the body of a HTTP response.
5. The HTTP response is sent to the web client.
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<html>
<head>
<title>Basic PHP Page</title>
</head>
PHP Script is embedded within
<body>
<?php … ?> in a text file .
<?php
echo "Hello World!";
?>
- Typically store in a file with the
extension .php
<hr>
- Usually inter-weaving with HTML
codes
<?php echo "How are you?"; ?>
</body>
</html>
A PHP Script that output "Hello World".
PHP Tutorials (The Basics)
http://www.w3schools.com/PHP/default.asp
Output
Variables
Strings
Operators
Named Constants
Single vs. Double Quotation marks
Arrays
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…
<form action="form1.php" method="POST">
Name: <input type="text" name="name" /><br/>
<input type="submit" />
</form>
<hr />
<?php
// If the user reaches this page by submitting
// the name through the above form.
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
if (!empty($_POST['name']))
echo "Hello! " . $_POST['name'];
else
echo "Please enter a name";
}
?>
<br />
…
form1.php: Retrieving and displaying form data
Retrieving Form Data
PHP made available the form data embeded in a
HTTP request through several supergobal arrays:
$_POST
Contains form data sent via the POST method
$_GET
Contains form data sent via the GET method
$_REQUEST
Union of $_GET, $_POST, and $_COOKIE
Convenient to use but not secure (why?)
Other Superglobal Arrays
$_FILES
Contains data sent via the HTTP POST file upload
$_COOKIE
Contains cookies embedded in the HTTP header
$_SESSION
Stores data within a script's session
$_ENV
Contains data provided by the environment
$_SERVER
Contains data set by the web server (e.g., server's name, version,
etc.)
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…
<form action="form2.php" method="GET">
<select name="list1[]" multiple="true" size="3">
<option value="Value 1">List Item #1</option>
<option value="Value 2">List Item #2</option>
<option value="Value 3">List Item #3</option>
</select>
<input type="submit" />
</form>
<hr />
<?php
if (is_array($_GET['list1'])) {
foreach ($_GET['list1'] as $value)
echo $value . "<br />";
}
?>
…
form2.php: Retrieving multiple data from a list or check boxes
Checking for Omitted Input
If a text field, password field, or text area is blank,
an empty string is assumed to be its value.
i.e., the corresponding variable name will still appear in
the query string as
name1=&name2=
If a user does not
Click a button
Select any item from a selectable list
Check a radio button or check box
the corresponding variable is not returned
i.e., the corresponding variable name won't appear in the
query string.
Checking for Omitted Input
isset($var) is false if and only if $var is NULL.
i.e., either $var does not exist or is never assigned a
value.
Use this function to check if a form variable exists
Use this function to check if a check box, radio button,
button, or a selectable list has a value
empty($var) is true if $var is 0, empty string,
NULL, or FALSE.
Use this function to check if a text field, password field,
or text area has a value that is not an empty string.
Checking the data type of a variable
is_array($var) is true if and only if $var is an
array.
is_numeric($var) is true if $var is a
numerical-type variable or a string containing a
valid numeric value.
Use this function to check if a value entered in a form is
a number or not.
Other type validating functions:
is_bool(), is_float(), is_int(),
is_null(), is_resource(), is_scalar(),
is_string()
Making Sticky Form
A sticky form is simply a standard HTML form that
remembers how you filled it out.
Text field example:
<input type="text" name="city" size="20"
value="<?php echo $_POST['city']; ?>" />
Selectable list example:
echo '<select name="year">';
for ($y = 2008; $y <= 2018; $y++) {
echo "<option value=\"$y\";
if ($year == $y)
Can you give an
echo ' selected="selected"';
example when you
echo ">$y</option>\n";
should use a sticky
}
form?
echo '</select>';
Using External Files
include() and require()
Insert the content of a file into the script that calls the function.
e.g.,
include('header.ihtml');
include('C:/php/abc/file.php');
Can be used to include header, menu, footer of a web site.
When include() fails, it output a warning message but the script
will continue to run.
When require() fails, it output a warning message and the script
is halted.
include_once() and require_once()
Only include/insert the content of a file once per request.
Usually used to include PHP library codes.
Forwarding the request to another PHP file
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<?php
// User has not yet logged in
if (…) {
// Show the login page instead
include("login.php");
exit();
// Return immediately
}
// Otherwise proceed with displaying the file content
?>
<html>
…
</html>
Anything output before calling include() will remain in
the output.
The URL shown in the web client will be the URL of the
above file and not the URL of login.php.
