1. PHP
Reusing Code and
Writing Functions

2. Reusing Code. Functions.
Topics:
Code inclusion using require() and include()
Defining functions
Managing function parameters
Passing-by-reference vs. passing-by-value
Parameters default values
Variable-length parameter lists
Understanding variable scope in functions
Using functions to return values
Using recursive functions
Anonymous functions

3. Reusing Code - why? Advantages: Reduces costs Increases reliability
Reusing eliminates time spent to design, code, test, debug a new piece of software.
Increases reliability
Existing, mature code is usually more reliable than new code: it has already been thoroughly tested, possible defects have been discovered during testing (and use), and have been fixed.
Improves consistency
Existing code is already consistent with the other parts of the system: in terms of user interfaces, interfaces with other systems.

4. Modularity - why? … has a favorable impact on program development:
Allows program to be divided into logical pieces:
Level of difficulty grows with the size and complexity of a program
Divide work among programmers
Easier to debug when modules are tested alone fully first, then integrated systematically
Easier to read, especially when commented correctly.
Easier to modify, isolating modules to change
Allows for reuse (avoiding redundant code); when an algorithm or computation is done over and over, it can be put in a method.

5. Code Inclusion
PHP allows to reuse any type of code (not only functions, classes):
Can insert code from a file into your PHP script with include (‘filename’); require (‘filename’);
Statements include() & require() are similar, except when they fail:
include() construct just gives a warning if failing to include file
require() construct gives a fatal error, that will cause program to terminate
Can also use variations include_once() or require_once() to avoid problems with redundancy; ex. redefining same function
Slower than include()/require()

6. Fail_include.php

7. Code Inclusion
The files loaded using include / require can contain everything that is normally used in a PHP file: PHP statements, PHP functions, PHP classes, HTML code, client-side scripting
PHP code still has to be placed within PHP tags
Filename extensions:
When include()/require() is used in a PHP script: the loaded file becomes part of the PHP script and is executed as such → as if the loaded file’s contents replaced the include()/require() statement
PHP does not look at the filename extension of an included file
 include files can have any extension, if not to be used directly.
Usually: .php or .inc (note: if located in the web document tree, their content can be seen in clear!)

8. Main.php

9. Home.html

10. Code Inclusion
The include files can be dynamic and generate on-the-fly parts of the page
Apache or PHP can be configured to automatically load specific pages / files before and after every page, even for individual directories (applications)
 include() statements not needed in this case
Not on cscdb…