php中构造函数的作用是什么

class Preson{
public $name; //定义变量
public $age;
public $sex;
public $height;
function __construct($name,$age,$sex,$height){
$this->name = $name; //为变量赋值
$this->age = $age;
$this->sex = $sex;
$this->height = $height;
}
public function PlayBaskteBall(){
if($this->height>175 || $this->age < 22){
return $this->name . "可以打篮球";
}else{
return $this->name . "不具备打球的条件";
}
}
}
$Preson1 = new Preson("大白","20","女","180");
echo $$Preson1->PlayBaskteBall();