PHP Variables

Variables in PHP

Variable is nothing it is just name of the memory location.
A Variable is simply a container i.e used to store both numeric and non-numeric information.

Rules for Variable declaration

• Variables in PHP starts with a dollar($) sign, followed by the name of the variable.
• The variable name must begin with a letter or the underscore character.
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
• A variable name should not contain space

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Assigning Values to Variables

Assigning a value to a variable in PHP is quite east: use the equality(=) symbol, which also to the PHP’s assignment operators.
This assign value on the right side of the equation to the variable on the left.
A variable is created the moment you assign a value to it:

Eg i

 <?php
  $myCar = "Honda";
  echo $myCar;
  ?>

 Output : Honda

In the above example
Create a variable ($mycar)containing a string with value=”Honda”.
To print the carname pass $mycar inside echo statement.

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PHP Concatenation

Eg ii (concatenate variable with string)

   <?php
  $myCar = "Honda City";
  echo $myCar." is riding";
 
       ?>

     Output: Honda City is riding
  

In the above example

Variable($mycar) hold value=”honda city”. Now we wants to concatenate variable with string.

pass this variable($mycar) inside echo statement.

To concatenate this with a string(“is riding”) use dot(.) between variable name and string.

The output will be displayed : Honda City is riding

Eg iii (Sum of two numbers)

     <?php
  $first = 100;
                $second = 200;
                $third = $first + $second;  
  echo "Sum = ".$third;
 ?>

    Output: Sum = 300  

In the above example
Declare $first , $second variable with value=100, 200 respectively.
Now add these two numbers using arithmetic operator (“+”).
sum of these two variable result stored in a third variable($sum).
Now print the sum passing ($third) with echo statement with a string.

Eg iv (Subtraction of two numbers)

     <?php
  $first = 1000;
                $second = 500;
                $third = $first - $second;  
  echo "Subtraction = ".$third;
 ?>

 Output : Subtraction = 500
  

In the above example
We perform subtraction using variables( $first, $second) with vale=1000,500.
Subtract second variable from first, result is hold by third variable($third) .
Print this third variable passing with echo statement.

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Destroying PHP Variables

To destroy a variable, pass the variable to PHP’s unset( ) function.

as in the following example:

Eg v

  <?php 
 $name="steve";
 echo $name;
  //unset( ) function destroy the variable reference.
 unset($name); 
   ?>

    Output: steve  

In the above example
declare variable $name hold value=”steve”. In this program we used unset() function to delete a particular variable.
first it show the output: “steve”, because we pass unset function after echo statement.
Now pass variable name inside unset($name) function output will show an Notice error(Variable is undefined).

Eg vi

  <?php 
 $first = 100;
 $second = 200;
        $third = $first + $second;
 echo "Sum = ".$third;
 unset($third);
       //after delete the variable call it again to test
         echo "Sum = ".$third; 
  ?>

  Output: Sum = 300
 Notice error undefined third variable 

Note : Trying to access or use a variable that’s been unset( ), as in the preceding script, will result in a PHP “undefined variable” error message.
This message may or may not be visible in the output page, depending on how your PHP error reporting level is configured.

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Variable names in PHP are case-sensitive

<?php
$name="rexx";
$NAME="rahul";
echo $name."<br/>";
echo $NAME;
?>

Output :rexx
       rahul

Variable names in PHP are case-sensitive. As a result, $name refers to a different variable than does $NAME.

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Inspecting Variable Contents(Variable Property)

PHP offers the var_dump( ) function, which accepts a variable and X-rays it for you.

Here’s an example

Eg vii ( For String value )

 <?php
//define variables
$name = "Fiona";
$age=25;

//display variable contents
var_dump ($name);
var_dump($age);
   ?>

  Output : string 'Fiona' (length=5)
  int 25

In the above example
We use var_dump( ) function to check the Contents(property) of variable, $mycar hold value =”Honda City”.
Now pass this variable inside var_dump($mycar) function .
It show all information related this(data type of variable, length(only string), value)

Eg viii ( For Integer values )

     <?php
  $first = 100;
         $second = 200;
                $third = $first + $second;
  var_dump ($third);
 ?>

 
     Output : int 300

Eg ix ( For Floating value )

     <?php
  $first = 100.5;
         $second = 200.2;
                $third = $first + $second;
  var_dump ($third);
 ?>

 Output :  float 300.7  

In the above example
variables first hold $first=100.5, second hold $second=200.2.
Now add these two values, result is stored in third variable($third).
Pass this variable inside var_dump($third) to check the content.
output will float 300.7

Eg x ( For Boolean value )

     <?php
  $bool = true;
         var_dump ($bool);
 ?>

 Output : Boolean true  

In the above variable
$bool with value=”true”. var_dump($bool) function is used to display the result
so output will display Boolean true, because variable holds a Boolean value