PHP –Writing Reusable Code 10 March 2006 Adina Crainiceanu adina IT420: Database Management and...
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PHP –Writing Reusable Code 10 March 2006 Adina Crainiceanu www.cs.usna.edu/~adina IT420: Database Management and Organization
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Transcript of PHP –Writing Reusable Code 10 March 2006 Adina Crainiceanu adina IT420: Database Management and...
PHP –Writing Reusable Code10 March 2006
Adina Crainiceanu
www.cs.usna.edu/~adina
IT420: Database Management and Organization
Goals Today
Writing Reusable code External files Functions
Typical Function Presentation
string date (string format [, int timestamp])
Return type
Function name
Parameter type
Parameter name
Optional parameter(s)
Calling a Function
$todayDate = date(“d F y”);
Note: Function names are NOT case sensitive Variable names are case senstive
Writing Reusable Code
Example: Typical page header:<html><head>
<title> My Page Name </title></head><body bgcolor=“#FFFFF”>
Type same code for every page? What if want to change bgcolor?
Include files
Write code once and save it into a file Include the file in every page Example: header.php
<html>
<head>
<title> <?php echo $pageTitle; ?> </title>
</head>
<body bgcolor=“#FFFFF”>
Include example (cont)
index.php
<?php
$pageTitle = “Adina’s Page”;
include (“header.php”);
echo “Some content for my page”;
?>
Generated HTML Page
<html>
<head>
<title> Adina’s Page </title>
</head>
<body bgcolor=“#FFFFF”>
Some content for my page
Include Functions
include(string fileName) Includes the content of fileName into current
file
require(string fileName) Like include() Fatal error if fileName not found!
include_once(string fileName) require_once(string fileName)
Class Exercise
Write the code for a footer in a file Include it in index.php file, to obtain a well-
formed HTML document
User-Defined Functions
Define functions to performs repetitive tasks
Examples: Open a database connection and select a
database Display the elements of an array as a table …
Define a Function
function my_function() {
echo ‘This is printed by my function’;
}
Keyword to define a function
Function name
Function code
Calling the Function
<?php my_function(); ?>
Result:
This is printed by my function
Function Parameters
function my_function($text) {
echo $text;
}
Call: my_function(“Print this text”);
Result: Print this text
Optional Parameters
function my_function($text=“Default text”) {echo $text;
}
Call: my_function(“Print this text”); Result: Print this text Call: my_function(); Result: Default text
Multiple Optional Parameters
function start_table($border, $cellspacing=2, $cellpadding=2){
echo “<table border = $border cellspacing = $cellspacingcellpadding = $cellpadding>”;
} start_table(1) equivalent start_table(1,2,2) start_table(2,3) equivalent start_table(2,3,2) start_table(2,3,4) Parameter values filled in from left to right!
Return Values
function add_values($a, $b){$result = $a + $b;
return $result;
}
Call: $added_val = add_values(4,5); Result: $added_val has value 9
Class Exercise
Write a function is_leap to test whether a yar is a leap year or not
Return “Yes” if input parameter is leap year
Return “No” if input parameter is not a leap year
Variables Scope
Variables declared in functions are visible from declaration line to end of function – local variables
Variables declared outside functions are visible from declaration line to end of file, but not inside functions – global variables
Superglobal variables ($_POST, $_SERVER, …) are visible everywhere
Keyword global makes local variables global – not recommended
Variables Scope Example
function fn(){$var = ‘content’;
}
fn();
echo $var;
Result? Nothing is printed!
Variables Scope Example 2$var = ‘content 1 <br/>’;echo $var;function fn(){
echo $var;$var = ‘content 2 <br/>’;echo $var
}fn();echo $var;
Result?
content 1content 2content 1
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
Class Exercise
Write the PHP script to use my_dbconnect Connect to localhost Default user and password Select database vp5fund
