示例程式碼

<?php
error_reporting(-1);
ini_set('display_errors','on');

class A { 
    public $a = 'hello';

    public function add() {
        $this->b = 'world';
    }-  
    public static function p() {
        echo 'world',PHP_EOL;
    }-  
}

$a = new A;
$a->add();
$a->c = 'test';
$a->p();

var_dump($a);
 

world
object(A)#1 (3) {
  ["a"]=>
  string(5) "hello"
  ["b"]=>
  string(5) "world"
  ["c"]=>
  string(4) "test"
}

$a->p();