Best Practices cont

1
Best Practices (cont)

• Philip Windridge

2
Contents

• A bit on bottlenecks
• Consider your code
• Caching and PEAR
• Functions and External Files

3
Performance consideration

• Performance is application specific
• It involves
• Processor
• Memory
• Network
• Coding style
• Maintainability

4
Expensive Code

• More expensive
• for(i 0 i lt (strlen(string) - 1) i)
  //Do something
• for(i 0 i lt myArraymyValue i) //Do
  something
• Less expensive
• string_len (strlen(string)-1)
• for(i 0 i lt string_len i) //Do
  something
• arrayValue myArraymyValue
• for(i 0 i lt arrayValue i) //Do
  something

5
Caching

• Initialise
• Determine book details to view
• Retrieve data from data base
• Create and output html

• Initialise
• Determine book details to view
• Check cache for already generated html
• Yes?
• Output cached html
• No?
• Retrieve data from data base
• Create and output html
• Cache html

6
PEAR

• PHP Extension and Application Repository
• A structured library of open-sourced code for PHP
  users
• A system for code distribution and package
  maintenance
• A standard style for code written in PHP,
  specified here
• The PHP Extension Community Library (PECL)
• A web site, mailing lists and download mirrors to
  support the PHP/PEAR community

(http//pear.php.net/manual/en/introduction.php)
7
Recap

• Hardware vs. software issues
• Optimisation vs. ease of maintenance/ readability

8
Improving Your Code

• Use functions where code can be generalised
• Use separate files for PHP where common code will
  be used across multiple pages

9
Improving Your Code

• Code available within the page
• User defined functions
• Code available across a number of web pages
• include
• require
• include_once
• require_once

10
Wk3 Exercise 1

• Create a PHP form that will accept a percentage
  grade and convert it to the appropriate grade
  point. There are separate scales for
  undergraduate awards (BSc, HND/C) and
  postgraduate awards (MSc, MRes). Your form should
  accept a percentage value between 1-100 and what
  level the grade belongs to.

11
Wk 3 Exercise 3

• Create a form that can accept ten string values.
  Upon posting this form with ten completed values,
  have the contents of the fields placed into an
  array. Output the array to the browser, sort
  ascending and output then sort descending and
  output. You may sort the array in any way you see
  fit.

12
Wk3 Exercise 4

• Create a copy of exercise three and modify it so
  that it asks for the number of elements to be
  input (Hint use a loop to output form elements
  according to user choice). Start with a default
  of 10 text inputs. Produce the same output as
  exercise three with the variable number of array
  values. This exercise should, ideally, involve
  much of your exercise three solution.