Question

I have a very simple question, but I’d like to know :
When and why it’s better to use simple functions, and when and why it’s better to use classes?

Answer 1

I have simple answer:

Use classes when you need to treat with objects, especially when you need to persist data while calling functions.

Use simple function when you have just output from input, without accessing any other variables.

Example:

class Basket {
  private $apples = 0;

  public function fill() {
    $this->apples = 100;
  } 

  public function take($count) {
    $this->apples -= $count;
  } 

  public function applesInBasket() {
    return $this->apples;
  }
}

versus

/* simple */ function wrap_with_div($content) {
  return "<div>$content</div>";
}