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HTML Forms & PHP

COMP284 Lectures

Web Applications using PHP

flowchart LR
Browser -->|1. Post Action| ws[Web Server]
ws -->|2. Process| pp[PHP Processor]
pp <-->|3. Store/Retrieve| ds[Database Server]
pp -->|4. Merge with HTML| ws
ws -->|5. Return HTML| Browser

PHP & Forms

We can use something like the following to call a php script with the restult of a form:

<form action='process.php' method='post'>
	...
</form>

The following information is available to PHP scripts:

  • Information about the PHP environment.
  • Information about the web-server and client request.
  • Information store in files and databases.
  • Form Data
  • Cookie / Session Data

  • Date & Time (date formatting):

      date('H:i l, j F Y')	// 12:20 Thursday, 8 March 2022
  time() // Unix time in seconds

PHP Environment

phpinfo([part])

Displays information abou the PHP installation and EGPCS data (environment, GET, POST, cookie and server data).

  • The optional part argument can take the following options to only display certain information:
    • INFO_GENERAL - The configuration, php.ini location, build date and web-server.
    • INFO_CONFIGURATION - Local and master vales for PHP directives.
    • INFO_MODULES - Loaded modules.
    • INFO_VARIABLES - All EGPCS data.

Manipulating the PHP Configuration

The following function can be used to access and change the configuration of PHP from within the PHP script:

Function Description
ini_get_all() Returns all the registerd configuration options.
ini_get(option) Returns the value of the configuration option option.
ini_set(option, value) Sets the value of the given configuration value. The configuration option will keep this new value during the script’s execution and will be restored after.
ini_restore(option) Restores a given configuration option to its original value.

We can use this to show errors in the HTML output:

<html lang='en-GB'>
<head></head>
<body>
<? php
	ini_set('display_errors', 1);
	error_reporting(E_ALL | E_STRICT); // choose one
	echo '<p>The value of 1 divided by 0 is ' , 1/0 , '</p >';
?>
</body>
</html>

Server Variables

The superglobal $_SERVER array stores information about the web-server and the client request.

A full list of keys are available here: http://php.net/manual/en/reserved.variables.server.php.

Form Data

The form data is passes to a PHP script via three superglobal arrays:

Variable Description
$_POST Data from the POST client requests.
$_GET Data from the GET client requests.
$_REQUEST Combined data from POST and GAT client requests. Equivalent to cgi.FieldStorage() in Python CGI.

We can access data by the name:

$_REQUEST['username']

String Functions

The following functions could be useful when processing form data:

Function Description
strtolower(str) Returns a string will all alphabetic characters in str converted to lower-case.
substr(str, start [,length]) Returns the portion of the string str starting at position start and consisting of at most length characters. If start is negitive, the returned string will start at the start‘th character from the end of the string.
date(format, [,timestamp) Returns a string formatted according to the given format string format using the given timestamp or the current time if no timestamp is given.

HTML Form Example

There is a full example for generating and processing a HTML form using PHP starting at slide 14

The following form is used:

POST, Redirect, GET (PRG)

As we used a POST request, if a person refreshes the page, this can resend the request giving unwanted side effects.

This design pattern requires that we:

  • Redirect to a results page after a POST request.

There is an example of extending the original form with this functionality starting at slide 21