why we use constructor in php code example

Example 1: php 8 constructor

class Point {
  public function __construct(
    public float $x = 0.0,
    public float $y = 0.0,
    public float $z = 0.0,
  ) {}
}

Example 2: php __construct

public function __construct(){}

Example 3: php constructor

__construct ([ mixed $args = "" [, $... ]] ) : void