Transcript ISP566/666 Week 6

Web Database Programming
Week 6
Using Templates
&
Updating Web Database
PHP & HTML
• PHP code can be inserted anywhere in HTML
code
• PHP code can output any HTML code
• Tightly mixed code (e.g. our sample code)
– Hard to read
– Hard to maintain
– What if you want to change the appearance of the
page?
– What if you decide to use a different algorithm?
Separate Presentation and
Processing
• An important user interface design
principle
– Easy to change interface or backend
processing independently
– Easier maintenance
– Reusable code
• How?
– Using templates
Template
• Define HTML presentation
• Placeholders
– To be filled with data from PHP code
• Extensions to PHP
– Smarty
– PEAR Integrated Template
PEAR
• PHP Extension and Application
Repository
– Includes many packages
• DB, HTML_Template_IT, Authentication,
Encryption, Graphics, XML, SOAP…
– Core packages comes with PHP 4.3.0 later
– Optional packages needs to be installed
HTML_Template_IT Template
• http://pear.php.net/manual/en/package.
html.html-template-it.php
• Template Format:
– Regular HTML
– Placeholder
{placeholder_name}
– Block
<!-- BEGIN block_name -->
<!-- END block_name -->
HTML_Template_IT Class
• Use the class
require_once “HTML/Template/IT.php”
• Create the object
$template = new HTML_Template_IT(“template_dir”);
• Call the methods
$template->loadTemplatefile(“template_filename”,
true, true);
$template->setCurrentBlock(“block_name”);
$template->setVariable(“placeholder_name”, data);
$template->parseCurrentBlock();
$template->show();
Update Database
• Table Operations
– Create table structure
– Change table structure
– Delete table
• Record Operations
– Insert a record to a table
– Update a record
– Delete a record
Making an Insert Form
• Example
• Notes
– Recall that PHP will convert form field
names into variables in the action page
– use input type=hidden to set predefined
and previously fixed values (like foreign
keys); and to carry values forward
Using SQL for Insert
• SQL
INSERT INTO tablename (columnnames)
VALUES (values)
• Note
– value do not have to come from form –
they could, for example, be computed, or
taken from another query
– Remember ‘single quote’ for text values
and not for numbers
An Update Form
• Example
• Notes
– note the addition of a record ID value
(which we must get from somewhere!);
tells us which record we are updating.
Using SQL for Update
• SQL
UPDATE tablename
SET columnname = value, ...
WHERE condition
• Notes
–value are set on all records
matching the condition!
Deleting data from a table
• The form for the SQL part of the code is:
DELETE FROM tablename
WHERE condition
• Note:
– all records matching the condition are
deleted
– if there is no where clause deletes all
records in table