In programming, a variable is a value that can be changed. All variables will have a storage location and a name. The variable name is usually used to refer the value that is stored in a variable.
Declaring variables in PHP
In PHP, variables are denoted with a $ symbol preceding the variable name.
Example
<?php
$a = "Hello world!";
$x = 5;
$y = 10.5;
$z = 'a';
?>Things to remember
- PHP automatically converts variables from one type to another.
- A variable will have a value of it’s most recent assignment.
- Variables do not need to be declared before assigning a value.
- Values are assigned to a variable using the = operator.
- A variable name cannot start with a number.
- Variable names are case-sensitive.
- When assigning text to a variable, put the value in a quote.
Scope of a variable
The scope of a variable refers to the accessible range of a variable in a program. In PHP, there are mainly two different variable scopes.
- Local – The variable is only accessible within the function that created it.
Example
<?php
$a = 1; /* global scope */
function localVar()
{
$a=10;
echo "The local variable a has value: $a"; /*local scope variable */
}
localVar();
echo "The global variable a has the value: $a";
?>The above program when executed will produce the following output.
The local variable a has value: 10
The global variable a has the value: 1
- Global – A global variable can be accessed from anywhere in the program. To access a global variable in a function, you should use global keyword.
Example
<?php
$a = 1;
$b = 2;
function my_function()
{
global $a;
$b=5;
echo "The value of a is $a";
echo "The value of b is $b";
}
my_function();
echo "I am having the value $b";
?>The above program when executed will produce the following output.
The value of a is 1
The value of b is 5 I am having the value 2
