<?php
class testA{
    public $a = "";
    public function __construct($a)
    {
        $this->a = $a;
    }
    public function test1($a=""):string{
        return (string)$this->a." ".$a."<br>\n";
    }
    public function test2($a=""):string{
        return (string)$this->a." ".$a."<br>\n";
    }
}
class test{
    public function main($a="Hello"):object
    {
        $this->a = $a;
        return new testA($this->a);
    }
}
$test = new test();
print $test->main()->test1("PHP");
print $test->main("by")->test2("C");

<?php
    class test{
        function main(){
            return new class{
                function testA(){
                    return "testA";
                }
                function testB(){
                    return "testB";
                }
            };
        }
    }
    $test = new test();
    print $test->main()->testA();
    print $test->main()->testB();