PHP Chapter 2 Variables

Chapter 2 Variables

•          A variable is a container that’s used to store both numeric and non-numeric info.
•          Use a dollar ($) symbol in front
•          Must begin with letter or underscore
•          No commas question marks, spaces or periods
•          =  Assign the value to the right side of the equation to the variable on the left
•          Variable names in PHP are case-sensitive.

Example 1

<?php

$name = 'Janine';

echo "welcome to $name 's Blog";

?>

Download here:  https://docs.google.com/file/d/0B7SlVynBEEAbaFJHWDBBM3BTMTQ/edit

Example 2

<?php

// assign value to variable

$now = 2012;

// assign variable to another variable

$currentYear = $now;

// perform calculation

$lastYear = $currentYear - 1;

// output: '2011 has ended. Welcome to 2012!'

echo "$lastYear has ended. Welcome to $currentYear!";

?>

Download here:  https://docs.google.com/file/d/0B7SlVynBEEAba1dRazBHa2hLNGs/edit

Example 3

How to set a variable’s name dynamically

<?php
// set a variable
$attribute = 'oranges';
// create a new variable
// its name comes dynamically
// from the value of $attribute
${$attribute} = 200;
// output: 200
echo $oranges;
?>

Download here: https://docs.google.com/file/d/0B7SlVynBEEAbRGU3NXJteDF5RHc/edit

Destroying Variables

•   unset() function

Example 4

<?php

$car = 'Porsche';

// output: 'Before destroying, my car is a Porsche'

echo "Before destroying, my car is a $car";

// destroy variable

unset($car);

// print variable value

// this will generate an 'undefined variable' error

// output: 'After destroying, my car is a '

echo "After destroying, my car is a $car";

?>

Download here: https://docs.google.com/file/d/0B7SlVynBEEAbS0VDS3piR2ctTmc/edit

•  This will result in an undefined variable error message.
•   This message may or may not be visible in the output page.
•   Alternatively, empty a variable of its contents by assigning PHP’s special NULL
•    $car = NULL;

Var_dump()

• Used to display structured information (type and value) 
•  print_r() function  performs  same function as var_dump(),although it returns less information.

Example 5

$number=678;

Echo var_dump($number);

//Output int(678) 

$name="janine";

Echo var_dump($name);

//Output string(6) "janine"

Download here: https://docs.google.com/file/d/0B7SlVynBEEAbTGJ2Z2N1bVJXdzg/edit

Data Types

Boolean

·         1(true) or 0 (false) values

Example

$validAge = true;

 Integer

·         A whole number

Example

$age = 15;

Floating point

·         A number that includes decimal places, such as 5.24 or 123.456789.

·         This is often called a real number or a float.

Example

$temp = 99.6;

String

·         A series of single characters

Example

$cat = 'Garfield';

Null

·         Empty variables

·         variable without any data

Example

$train = null;

PHP support numbers written in hexadecimal, octal, or scientific notation

<?php

// 8, specified as octal value

$a = 010;

// 1500, specified as hexadecimal value

$b = 0x5dc;

// 690, in scientific notation

$c = 6.9E+2;

?>