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In PHP, variables can have different scopes, and there are several types of variables based on their scope and behavior. The most common types are as given bellow.
Local Variables :
- Local variables are declared inside a function and have local scope, meaning they are only accessible within that function.
- They are not accessible from outside the function or in other functions.
- Local variables are temporary and are destroyed when the function’s execution ends.
function myFunction() {
$localVar = "I am local";
// $localVar is only accessible within myFunction
}
Global Variables :
- Global variables are declared outside of any function and have global scope, meaning they are accessible from anywhere in the script, including inside functions.
- To use a global variable inside a function, you need to use the
globalkeyword to declare it as global within the function.
function myFunction() {
$localVar = "I am local";
// $localVar is only accessible within myFunction
}
Note:
Be cautious when using global variables, as they can make code less modular and harder to debug.
Static Variables :
- Static variables are local variables that retain their value between function calls.
- They are declared with the
statickeyword inside a function and are initialized only once when the function is first called. - Static variables are useful when you want a variable to persist its value across multiple function calls.
function counter() {
static $count = 0;
$count++;
echo $count;
}
counter(); // Outputs: 1
counter(); // Outputs: 2
Superglobals :
- Superglobals are predefined global arrays in PHP that are accessible from anywhere in the script without the need to declare them as global.
- Some common superglobals include
$_GET,$_POST,$_SESSION,$_COOKIE,$_SERVER, and$_GLOBALS. - They are typically used to retrieve information such as form data, server information, or session data.
$username = $_POST['username'];