In PHP, variables are used to store and manipulate data. Variable names in PHP are case-sensitive, meaning $name and $Name are considered different variables. Here are some key points about PHP variables:

1. Variable Declaration:

   • Variables in PHP start with the $ (dollar) sign followed by the variable name.

   • Variable names must start with a letter or an underscore.

   • After the initial letter, variable names can contain letters, numbers, or underscores.

$variableName = "Hello, World!";

1. Data Types:

• PHP is a loosely typed language, meaning you don't need to declare the data type of a variable explicitly.

• Variable types are determined dynamically based on the content assigned to them.

$integerVar = 42;
$floatVar = 3.14;
$stringVar = "Hello";
$boolVar = true;

1. Variable Scope:

• PHP supports different variable scopes, such as global and local.

• A variable declared outside a function is considered global.

• Variables declared inside a function have local scope.

$globalVar = 10;

function exampleFunction() {
    $localVar = 5;
    echo $localVar; // Accessible within the function
}

echo $globalVar; // Accessible outside the function

1. Variable Concatenation:

• You can concatenate variables with the . (dot) operator.

$firstName = "John";
$lastName = "Doe";

$fullName = $firstName . " " . $lastName;

1. Variable Interpolation:

• When using double-quoted strings, variables are interpolated directly.

$name = "Alice";
echo "Hello, $name!"; // Outputs: Hello, Alice!

1. Variable Variables:

• PHP allows you to use a variable's value as the name of another variable.

$variableName = "count";
$$variableName = 5;

echo $count; // Outputs: 5

These are just some basic concepts related to PHP variables. Understanding these fundamentals will help you work with variables effectively in PHP.