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PHP Variable

Variables in PHP

Variables are nothing its just containers that hold data or information. In other, word variable are just identifiers.

Important point about PHP variable

  • It's used for storing information, like name, age place or anything.
  • For example, you create a variable, like $name and store the value 38.
  • The PHP variable names are case-sensitive.

PHP Variable Example

<?php

$variable = 15;

$variable_ab = 38;

$sum = $variable + $variable_ab;

echo " First value = ".$variable."
"; echo "Second value = ".$variable."
"; echo "sum = ".$sum; ?>

There are three variable in this example first is "variable", second is "variable_ab" and the third one is "sum". The value of variables displayed, perform an operation and store the value of on another variable named $sum and print.


Example of case sensitive variable


<?php

$a=7;

$A=38 ;

echo $a ."<br>";

echo $A;


?>

Output

7
38

$a and $A are not same as shown in the above example. Because PHP variable name are case sensitive.

Rules for Variable Declaration

There are some simple rules for creating a PHP variable.

  • A PHP variable must start with ($) dollar sign.
  • A valid PHP variable name start with underscore ( _ ) or alphabet.
  • The rest of variable name consist of alphanumeric character like acb1.
  • PHP variable can any length.
  • Uppercase letter is not equal to the lowercase letter.
  • Not contain spaces

PHP Variable Declaration

A variable is a named memory location that contains data that may be manipulated throughout the execution of the script.

Some valid variable example

  • $name
  • $programming_1
  • $_abc_variable
  • $m

Example of PHP Variable Declaration

<?php

$name="welcome to php";
// $12hj=12 //it's wrong 
echo $name;
echo "
"; // $@12hj=12 //its wrong $first_value=12.30; $d1=450; echo "The first value:".$first_value; echo "
"; echo "The second value:".$d1; echo "
"; ?>

You can create PHP variable anywhere by using the dollar sign in our PHP script.

In this example $name is a string variable, $first_value is the integer value and $d1 is a float variable.

Displaying variable values

The fastest way to display the variable value, using print_r statement.

Using print_r

   $name= "john";
print_r( $name ); 
   

using echo

   $name= "john";
echo 	( $name ); 
   

Example of variable declaration and initialization

<?php

$var="Display the value using echo" ;
$var1=" and print_r statements";
echo $var . $var1;
echo "
"; $first_value=12.30; echo $first_value; $d1=450; echo "
"; print_r($d1); ?>

The following characters are not allowed in variable name

  • asterisk (*)
  • plus(+)
  • hash(#)
  • minus(-)
  • ampersand(&)
  • at the rate(@)

Another way to create variable

It's another method to create a variable using string constant to create a dynamic variable instead of a general variable.

Syntax

 ${"name_of_variable"} = "value";
 

Example of variable declaration

<?php

$var = "Variable creation=";
${"user"} = "bob";
print_r($var);
echo $user;
echo "
"; $a = date("Y/m/d") . "
"; echo "Todays date= "; print_r($a); ?>

In this example we have explained the new way of creation of variable, $user is also a variable like other.

Delete PHP variable

You can use unset() function to destroy the variable. It takes one argument that is a variable name.

Delete variable example


<?php

	$brand = "Audi";

	echo $brand;

	unset($brand); 

?>

Output

Audi

In the above example $brand is a simple string type variable that hold the value Audi and print the variable and after use we can destroy the variable $brand an using unset function.

After destroying the variable, you cannot use that variable, if you use that variable, PHP displayed the notice like below shown.

Notice

Notice: Undefined variable: brand

Check type and length of variable

You can use var_dump( ) function to print the data type and the length of the variable as shown in below.

Check PHP Type Example

<?php

	$brand = "Audi";

	var_dump ( $brand );

?>

Output

string(4) "Audi"

You can also use gettype() function to check the type of variable.


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