PHP Variables
Variable is nothing it is just name of the memory location. A Variable is simply a
container that is used to store both numeric and non-numeric information.
Rules for Variable declaration
1. Variables in PHP starts with a dollar($) sign, followed by the name of the
variable.
2. The variable name must begin with a letter or the underscore character.
3. A variable name can only contain alpha-numeric characters and underscores (A-
z, 0-9, and _ )
4. A variable name should not contain space
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
<?php
$myCar = "Honda";
echo $myCar;
?>
Output- Honda
In the above example Create a variable ($mycar) containing a string with
value="Honda". To print the car name pass $mycar inside echo statement.
PHP Concatenation
Eg ii (concatenate variable with string)
<?php
$myCar = "Honda City";
echo $myCar . " is riding"; // dot(.) operator is used to concatenate mycar variable
and is riding
?>
Output- Honda City is riding
In the above example Variable($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.
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
Sum = 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.
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.
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, $name hold a string value ="Fiona" while $age hold an integer value = 25.
Now pass this variable inside var_dump($name,$age) 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