1. Web Programming– UFCFB3-30-1 Lecture 19-20
Instructor : Mazhar H Malik
Global College of Engineering and Technology

2. PHP Variables, Constants and Operators
Creating PHP Pages
PHP Variables, Constants and Operators

3. Basic PHP Variables
The values stored in computer memory are called variables
The values, or data, contained in variables are classified into categories known as data types
The name you assign to a variable is called an identifier

4. PHP Variables
Prefixed with a $
Assign values with = operator
Example: $name = “John Doe”;
No need to define type
Variable names are case sensitive
$name and $Name are different

5. PHP Variables Variables are not statically typed
Integers can become floats can become strings
Variable types include :
Boolean
Integer
Float
String
Array
Object
Resource
NULL

6. Assigned by reference, this links vars
PHP Variables
Assigned by value
$foo = "Bob"; $bar = $foo;
Assigned by reference, this links vars
$bar = &$foo;
Some are preassigned, server and env vars
For example, there are PHP vars, eg. PHP_SELF, HTTP_GET_VARS

7. Displaying Variables
To display a variable with the echo statement, pass the variable name to the echo statement without enclosing it in quotation marks :
$VotingAge = 18;
echo $VotingAge;
To display both text strings and variables, send them to the echo statement as individual arguments, separated by commas :
echo "<p>The legal voting age is ", $VotingAge, ".</p>";

8. Naming Variables
The name you assign to a variable is called an identifier
The following rules and conventions must be followed when naming a variable:
Identifiers must begin with a dollar sign ($)
Identifiers may contain uppercase and lowercase letters, numbers, or underscores (_). The first character after the dollar sign must be a letter.
Identifiers cannot contain spaces
Identifiers are case sensitive

9. Declaring and Initializing Variables
Specifying and creating a variable name is called declaring the variable
Assigning a first value to a variable is called initializing the variable
In PHP, you must declare and initialize a variable in the same statement:
$variable_name = value;

10. PHP Constants Constants are special variables that cannot be changed
Constant names do not begin with a dollar sign ($)
Use them for named items that will not change
Constant names use all uppercase letters
Use the define() function to create a constant
define("CONSTANT_NAME", value);
The value you pass to the define() function can be a text string, number, or Boolean value

11. Standard Arithmetic operators String concatenation with a period (.)
PHP Operators
Standard Arithmetic operators
+, -, *, / and % (modulus)
String concatenation with a period (.)
$car = “SEAT” . “ Altea”;
echo $car; would output “SEAT Altea”
Basic Boolean comparison with “==”
Using only = will overwrite a variable value
Less than < and greater than >
<= and >= as above but include equality

12. Assignment (=) and combined assignment
PHP Operators
Assignment (=) and combined assignment
$a = 3;
$a += 5; // sets $a to 8;
$b = "Hello ";
$b .= "There!"; // sets $b to "Hello There!";
Bitwise (&, |, ^, ~, <<, >>)
$a ^ $b(Xor: Bits that are set in $a or $b but not both are set.)
~ $a (Not: Bits that are set in $a are not set, and vice versa.)

13. Data Types
A data type is the specific category of information that a variable contains
Data types that can be assigned only a single value are called primitive types

14. Data Types PHP is not strictly typed
A data type is either text or numeric
PHP decides what type a variable is
PHP can use variables in an appropriate way automatically
E.g.
$vat_rate = 0.175; /* VAT Rate is numeric */
echo $vat_rate * “%”; //outputs “17.5%”
$vat_rate is converted to a string for the purpose of the echo statement
Object and Array also exist as types

15. Numerics Data Types PHP supports two numeric data types:
An integer is a positive or negative number and 0 with no decimal places (-250, 2, 100, 10,000)
A floating-point number is a number that contains decimal places or that is written in exponential notation (-6.16, 3.17, )
Exponential notation, or scientific notation, is a shortened format for writing very large numbers or numbers with many decimal places (2.0e11)

16. Boolean Values A Boolean value is a value of TRUE or FALSE
It decides which part of a program should execute and which part should compare data
In PHP programming, you can only use TRUE or FALSE Boolean values
In other programming languages, you can use integers such as 1 = TRUE, 0 = FALSE

17. References References :
Anonymous.(n.d.). Apache HTTP Server Documentation Version 2.2. Retrieved from
Achour, M., Betz, F. (n.d.), PHP Manual. Retrieved from
Anonymous. (n.d.). MySQL Reference Manual. Retrieved from
Naramore, E., Gerner, J., Le Scouarnec, Y., Stolz, J., Glass, M. K. (2005). Beginning PHP5, Apache, and MySQL® Web Development. Indianapolis, IN: Wiley Publishing, Inc.