PHP

1
IT420 Database Management and Organization

• PHP Writing Reusable Code
• 10 March 2006
• Adina Crainiceanu
• www.cs.usna.edu/adina

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Goals Today

• Writing Reusable code
• External files
• Functions

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Typical Function Presentation

• string date (string format , int timestamp)

Return type
Function name
Parameter type
Parameter name
Optional parameter(s)
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Calling a Function

• todayDate date(d F y)
• Note
• Function names are NOT case sensitive
• Variable names are case senstive

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Writing Reusable Code

• Example Typical page header
• lthtmlgt
• ltheadgt
• lttitlegt My Page Name lt/titlegt
• lt/headgt
• ltbody bgcolorFFFFFgt
• Type same code for every page?
• What if want to change bgcolor?

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Include files

• Write code once and save it into a file
• Include the file in every page
• Example header.php
• lthtmlgt
• ltheadgt
• lttitlegt lt?php echo pageTitle ?gt lt/titlegt
• lt/headgt
• ltbody bgcolorFFFFFgt

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Include example (cont)

• index.php
• lt?php
• pageTitle Adinas Page
• include (header.php)
• echo Some content for my page
• ?gt

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Generated HTML Page

• lthtmlgt
• ltheadgt
• lttitlegt Adinas Page lt/titlegt
• lt/headgt
• ltbody bgcolorFFFFFgt
• Some content for my page

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Include Functions

• include(string fileName)
• Includes the content of fileName into current
  file
• require(string fileName)
• Like include()
• Fatal error if fileName not found!
• include_once(string fileName)
• require_once(string fileName)

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Class Exercise

• Write the code for a footer in a file
• Include it in index.php file, to obtain a
  well-formed HTML document

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User-Defined Functions

• Define functions to performs repetitive tasks
• Examples
• Open a database connection and select a database
• Display the elements of an array as a table

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Define a Function

• function my_function()
• echo This is printed by my function

Keyword to define a function
Function name
Function code
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Calling the Function

• lt?php my_function() ?gt
• Result
• This is printed by my function

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Function Parameters

• function my_function(text)
• echo text
• Call my_function(Print this text)
• Result Print this text

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Optional Parameters

• function my_function(textDefault text)
• echo text
• Call my_function(Print this text)
• Result Print this text
• Call my_function()
• Result Default text

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Multiple Optional Parameters

• function start_table(border, cellspacing2,
  cellpadding2)
• echo lttable border border
• cellspacing cellspacing
• cellpadding cellpaddinggt
• start_table(1) equivalent start_table(1,2,2)
• start_table(2,3) equivalent start_table(2,3,2)
• start_table(2,3,4)
• Parameter values filled in from left to right!

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Return Values

• function add_values(a, b)
• result a b
• return result
• Call added_val add_values(4,5)
• Result added_val has value 9

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Class Exercise

• Write a function is_leap to test whether a yar is
  a leap year or not
• Return Yes if input parameter is leap year
• Return No if input parameter is not a leap year

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Variables Scope

• Variables declared in functions are visible from
  declaration line to end of function local
  variables
• Variables declared outside functions are visible
  from declaration line to end of file, but not
  inside functions global variables
• Superglobal variables (_POST, _SERVER, ) are
  visible everywhere
• Keyword global makes local variables global not
  recommended

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Variables Scope Example

• function fn()
• var content
• fn()
• echo var
• Result?
• Nothing is printed!

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Variables Scope Example 2

• var content 1 ltbr/gt
• echo var
• function fn()
• echo var
• var content 2 ltbr/gt
• echo var
• fn()
• echo var
• Result?
• content 1
• content 2
• content 1

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Class Exercise

• Write a function my_dbconnect to open a db
  connection and select a database
• Input parameters
• db server name
• user name optional, default value root
• password optional, default value
• database name
• Return value
• FALSE if errors occurred
• database connection if everything OK

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Class Exercise

• Write the PHP script to use my_dbconnect
• Connect to localhost
• Default user and password
• Select database vp5fund