ITC 240: Web Application ProgrammingSUBHASH PRAJAPATI

04/09/15

Review• Client Server Architecture

• Server Side Language/ Client Side Language

• PHP Fundamentals/Syntax

• Variable

• Function

Today• More on Variables & Functions

• Scope

• Functions: parameters & returns, passing by values

• Conditionals

Variables• Container that can hold certain value (storing data into memory location)

• Starts with $ sign

• A noun

• Starts with underscore or letter

• Can be named with a-z, A-Z, _, 0-9 characters

• cAsE sEnSiTivE - $myVar and $Myvar are different

Functions• A block of code to perform a task

• Starts with “function” keyword

• A verb

• Can be named with a-z, A-Z, _, 0-9 characters

• NOT case sensitive – myfunction() & myFunction() are same, but good practice is just use one.

ConstantsAn identifier with an associated value which cannot be altered by the program during normal execution. Written in all UPPER_CASE

<?php

define ("SALES_TAX", .096);

$itemPrice = 50;

echo $totalPrice = $itemPrice + ($itemPrice * SALES_TAX);

?>

Variable Types• Boolean

$booleanVar = TRUE; // a boolean

• String

$stringVar = "foo"; // a string

$stringVar = 'foo'; // a string

• Integer

$integerVar= 12; // an integer

• Float

$floatVar= 12.5; // a floating point number

• Others: Array, Objects, Resource, Null (we’ll discuss later)

Function Types• User-defined Functions

The functions we define

• Build in Functions

The functions that come with PHP

for eg: date();

date ( string $format [, int $timestamp = time() ] )

// returns string

PHP date () functionA program to display today’s date

<?php

echo date (‘Y’); // displays the current year

echo date (‘m’); // displays the current month

echo date (‘d’); // displays today’s date

echo (‘H:i:s’); // Hour, minute, seconds

// automatic copyright

&copy; 2013-<?php echo date("Y")?>

?>

Check PHP date manual for complete list of the possible parameters

Class Exercise 2.1Write the output of following:

<?php

echo date('l jS \of F Y h:i:s A'). "<br>";

echo date(‘Y-m-d H:i:s’). "<br>";

?>

Class Exercise 2.2mktime (hour,minute,second,month,day,year) // returns unix timestamp

<?php

$date =mktime(10, 21, 45, 4, 11, 2012);

echo "Created date is " . date("Y-m-d h:i:sa", $date);

?>

Class Exercise 2.3strtotime (string) // pass English phrase

<?php

$date=strtotime("tomorrow");

echo date("Y-m-d h:i:sa", $date) . "<br>";

$date=strtotime("next Monday");

echo date("Y-m-d h:i:sa", $date) . "<br>";

$date=strtotime("+6 Months");

echo date("Y-m-d h:i:sa", $date) . "<br>";

?>

Class Exercise 2.3strtotime (string) // pass English phrase

<?php

$date=strtotime("tomorrow");

echo date("Y-m-d h:i:sa", $date) . "<br>";

$date=strtotime("next Monday");

echo date("Y-m-d h:i:sa", $date) . "<br>";

$date=strtotime("+6 Months");

echo date("Y-m-d h:i:sa", $date) . "<br>";

?>

Typecasting gettype ()/ settype() – built in functions

<?php

$foo = '1';

echo gettype($foo); // outputs 'string'

settype($foo, 'integer');

echo gettype($foo); // outputs 'integer‘

// another way

$a = (int) ‘55’;

?>

Typecasting

Operator Changes to

(int) Integer

(bool) Boolean

(string) String

(array) Array

(object) Object

(unset) NULL

User defined functions: Parameters

Parameters: arguments passed to a function

<?php function calculateSomething ($firstNumber, $secondNumber){

// do some calculations here}

?>

In above example, $firstNumber and $secondNumber are two parameters

User defined functions: Return Value

Return Value: the value returned by the function

<?php function addNumber ($firstNumber, $secondNumber){

$sum = $firstNumber + $secondNumber;return $sum;

}

?>

In above example $sum is the return value

User defined functions: Function Call

Function Call: Just defining the function does NOT do anything, until you call it.

function doSomeMagic ($magicName) {

// magic code here

}

// function call

doSomeMagic (‘awesome magic’);

Class Exercise 2.4 Write a program (a function) to converts Fahrenheit to Celsius temperature.

(for example 45.5 F = 7.5 C)

Formula:

C = ((F-32) * (5/9))

Celsius Scale: 0-100

Fahrenheit Scale: 32-212

Default parameter value <?php

function orderDrink ($drink = “coffee") { // coffee is the default value

return "Making a cup of $drink.\n";

}

echo orderDrink (“Ice Tea");

echo orderDrink ();

?>

User defined Functions: return Function can also return without the value

<?phpfunction returnInMiddle () {

// do something return;

// code written here will not be executed}

?>

Variable Scope The variables inside user-defined function have local scope.

Check output of following:

<?php

function addNumbers($a, $b){ $sum = $a + $b;return $sum;

}

echo $sum;

$sum = addNumbers (5,6);

echo $sum;

?>

Variable Scope The variables inside user-defined function have local scope.

Check output of following

<?php

$myName = “Tina”;

function printName(){ echo $myName;

}

printName ();

?>

Global Variable The variables inside user-defined function have local scope.

Check output of following

<?php

$a = 1;

$b = 2;

function addNumbers () {

global $a, $b;

$sum = $a+$b;

return $sum;

}

$sum = addNumbers ();

echo $sum;

?>

Passing by reference We can pass a variable by reference to a function so the function can modify the variable

<?php

function incrementTheVariable(&$var){

$var++;

}

$a=5;

incrementTheVariable($a); // $a is 6 here

?>