Important thing about variable 

Let’s first understand that what is variable? or what do you mean by variable? In general term variable means change-able or the capability which storing some data is known as variable. The data may be a number, string, array etc.

Important thing about variable in PHP

·         Like other programming language PHP doesn’t having data types like. (int, float, char, string, array etc..).

·         Its data type will be identifying through its value, means what value you store in PHP variable then that value will decide what type of variable is that.

·         Syntax                  $variable_name

·         every variable in PHP will start with a ‘$’ sign and then follow by variable name

·         In above example I declare two variable $name and $age, $name variable contain string type value and $age contain integer type value. 

·         If you want to know its data types then use “gettype()” method it we show the datatype

·         If you want to know data type with its value, then use “var_dump($varaiblename)” method

·                                     

Types of Variables

There are three different types of variable in PHP

·         Local:    Those variable which are created within function or block of code known as local variable. Local variable will not access outside of the function or block of code because it scope is bound within that function or block of code in which they are declared

·         Global: Those variable which are created outside the function or block of code and are known as global variable. global variable will be access within function or block of code and also outside the function or block of code. If you want to access any global variable inside the function or block of code, then to do this you have to explicitly say that it’s a global variable for this you have to declare variable with global keyword inside of the function or block of code.

·         Example: without global keyword

·         Static:   Those variable which are declare as static is known as static variable. The purpose of these static variable is to access local variable after function execution complete. Let’s see the code you will understand this very well

·         

Note: static variable will occupy memory once so they are alive till the program execution once you declare a variable as a static then if you change its value then its will be saved with previous value.

PHP Constants:

·         In PHP constant is a name or identifier for a simple value, that constant value never during the execution of the PHP script.

·         Constant values are very useful only when we want that the value of variable is never change in entire program

·          It will be very useful when we connect our web application with any database, once we initialize the database name to our application then its name will not be changed again.

·         To create constant in PHP, we will use define() function.

·         Constants are naturally global; you will access them inside or outside of the functions

·         Syntax 

.  Define(name, value, case-insensitive)

.   name:                           Specifies name of the constant variable

.   value:                            Specifies value of the constant variable

.   case-insensitive:      Specifies name of constant should be case-sensitive, by default case-sensitive is false

·         Example:  of constant

·          

PHP Echo and Print

        . Echo and print these two are different built-in function in PHP

        . Both are used to display data on the browser

        . Syntax of echo:                 echo()   or            echo “”; 

          .Syntax of print:                 print()   or            print “”;

         .Echo statements support multiple parameter and it is non-return type function

         . Print statements support only single parameter and it is return type function

·      

 PHP Operators

The thing which is used to perform some operation on variables or values is known as Operators

PHP support following type of operators.

·         Arithmetic operators

·         Assignment Operators

·         Comparison Operators

·         Increment/Decrement Operators

·         Logical Operators

Arithmetic operators

Simple algebraic operators are known as Arithmetic operators

Operator       Description              Result

+              Add two variables         $a+$b

-              Subtract two variables   $a-$b

*            Multiply two variables    $a*$b

/             Divide two variables       $a/$b

%          of two variables               $a%$b

Assignment Operators 

It is same like arithmetic but after performing arithmetic between to variables it stores the result to left hand variable

Operator	Description	Result
=	It is used to assign value	$x = $y
+=	It will add two variable then result will assign to left variable	$x+=$y or $x=$x+$y
-=	It will subtract two variable then result will assign to left variable	$x-=$y or $x=$x-$y
*=	It will multiply two variable then result will assign to left variable	$x*=$y or $x=$x*$y
/=	It will divide two variable then result will assign to left variable	$x/+=$y or $x=$x/$y
%=	It will remainder two variable then result will assign to left variable	$x%=$y or $x=$x%$y

Comparison Operators

Comparison operators are used to compare the two variables by its value and also by its data types

Operator         Name        Example       Result

==             Equal to         $x == $y          Return true if both are equal

!=            Not Equal to   $x != $y        Return true if both are not equal

===           Identical       $x === $y      Return true if both having same value and same datatype

!==          Not Identical  $x!== $y       Return true if both having same value or same datatype

<>           Not Equal to   $x<>$y       Return true if both are not equal to each other

<            Less than          $x<$y            Return true if $x has value less than $y

<=    Less than or equal to   $x<= $y   Return true if $x has value less or equal to $y

>        Greater than                $x>$y     Return true if $x has value greater than $y

>=  Greater than or equal to  $x>= $y  Return true if $x has value greater or equal to $y

Increment operator is used to increase the value by one and decrement operator is used to decrease the value by one.Increment/Decrement Operators

Operator          Name                    Description

$x++          Post-increment      First print the value then increment by one

++$a          Pre-increment     First increment the value by one then print

$x--           Post-decrement      First print the value then decrement by one

--$x           Pre-decrement      First decrement the value by one then print

Logical Operators 

Logical operators are used to valid the conditional statements

Operator     Name         Description

and              And             Return True if both variable are true          

or                Or                Return True if any one variable is true

xor              Xor               Return if either any variable is true not both

&&             And               Return True if both variable are true

||                  OR                Return True if any one variable is true

!                  Not                Return True if variable is false

 PHP Decision Making 

Decision making means make a suitable decision and execute that particular part of the program, so for decision making we use if, if else, if elseif and switch. Let’s understand these things in details

IF statements

When you want to execute the particular code then you can use IF statement, if statement is true then block of if statements will execute.

Syntax

                If(some conditions) {

                                Statements

                                statements

                }

IF Else statements

If “if statement” is true, then if statement block will execute otherwise else block will execute

Syntax

                If (some condition) {

                                Statements

                } else {

                                Statements

                }

IF ElseIf Else statements

It contains multiple if conditions, if any if statement is true the if that respected if block will execute otherwise else block will execute 

Syntax

                If (some condition) {

                                Statements

                } elseIf (some condition) {

                                Statements

                } else {

                                Statements

}

                                                                

Switch Statement

Switch statement is also used for decision making. It works same like “If Elseif Else” statement. In switch statement multiple case are defined, if any case match with user input then that matched case will be execute. If none of case will execute then default will execute. Default work like else block.

Syntax:

                Switch (input) {

                                Case n1:

                                                Statements;

                                break;

Case n2:

                                                Statements;

                                break;

Case n3:

                                                Statements;

                                break;

                                . . . . . .

                                default:

                                                Statements;

               

}