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";
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!";
?>
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
Download here: https://docs.google.com/file/d/0B7SlVynBEEAbTGJ2Z2N1bVJXdzg/edit
Data Types
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";
- 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;
?>
