Local and global variables in php with syntax and examples

In PHP, variables are used to store and manipulate data. There are two types of variables: local and global.

Local Variables:

- Declared within a function or block
- Only accessible within that function or block
- Destroyed when the function or block ends

Syntax:

function myFunction() {
  $localVariable = 'Hello, World!';
  echo $localVariable;
}


Examples:

function greet() {
  $name = 'John';
  echo "Hello, $name!";
}

greet(); // outputs "Hello, John!"
echo $name; // undefined variable


Global Variables:

- Declared outside of functions or blocks
- Accessible from anywhere in the script
- Persist until the script ends

Syntax:

$globalVariable = 'Hello, World!';
function myFunction() {
  global $globalVariable;
  echo $globalVariable;
}


Examples:

$greeting = 'Hello, World!';
function greet() {
  global $greeting;
  echo $greeting;
}

greet(); // outputs "Hello, World!"
echo $greeting; // outputs "Hello, World!"


Static Variables:

- Retain their value between function calls
- Only accessible within the function

Syntax:

function myFunction() {
  static $staticVariable = 'Hello, World!';
  echo $staticVariable;
}


Examples:

function greet() {
  static $greeting = 'Hello, World!';
  echo $greeting;
}

greet(); // outputs "Hello, World!"
greet(); // outputs "Hello, World!" again


Superglobals:

- Built-in global variables
- Accessible from anywhere in the script
- Examples: $_GET, $_POST, $_SESSION

Syntax:

echo $_GET['name'];


Examples:

// URL: (link unavailable)
echo $_GET['name']; // outputs "John"


Best Practices:

1. Use local variables for function-specific data.
2. Use global variables for shared data.
3. Use static variables for persistent data.
4. Use superglobals for built-in global variables.
5. Avoid using global variables when possible.
6. Use meaningful variable names.
7. Initialize variables before use.