What is the purpose of using isset in PHP functions?

When working with PHP functions, it is important to check if a variable is set before using it to avoid potential errors or warnings. The isset() function in PHP is used to determine if a variable is set and is not NULL. By using isset() in functions, you can ensure that the variable exists before attempting to use it, preventing undefined variable errors.

function exampleFunction($variable) {
    if(isset($variable)) {
        // Perform operations using $variable
        return $variable;
    } else {
        return "Variable is not set.";
    }
}