Variable Declaration In Php

Variables in PHP :

Variables are used for storing a values, like text strings, numbers or arrays. When a variable is set it can be used over and over again in your script All variables in PHP start with a $ sign symbol.

The correct way of setting a variable in PHP:

$var_name = value;

New PHP programmers often forget the $ sign at the beginning of the variable. In that case it will not work.

Let's try creating a variable with a string, and a variable with a number:

<?php
$txt = "Hello World!";
$number = 16;
?>

PHP is a Loosely Typed Language :

In PHP a variable does not need to be declared before being set.

In the example above, you see that you do not have to tell PHP which data type the variable is.

PHP automatically converts the variable to the correct data type, depending on how they are set.

In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.

In PHP the variable is declared automatically when you use it.

Variable Naming Rules :

• A variable name must start with a letter or an underscore "_"

• A variable name can only contain alpha-numeric characters and underscores (a-Z, 0-9, and _ )

• A variable name should not contain spaces. If a variable name is more than one word, it should be separated with underscore ($my_string), or with capitalization ($myString)

PHP case sensitive variable :

PHP variables are case sensitive so you cannot use $NAME as the place of $name.

//Example of PHP case sensitive variable
<?php
$name_of_car = "Audi R8";
echo $NAME_OF_CAR;
?>

//O/P : Notice: Undefined variable: $NAME_OF_CAR