preg_replace_callback - callback функция в классе не вызывается

class test {
public $w;

public function __construct(){}

private function t($q){
print_r($q);
return "sss".$q[1]."ddd";
}

public function e(){
$this->w=preg_replace_callback("{(qwerty)}","this->t","111qwerty222");
}

}


$test=new test();

$test->e();

echo "Hello!\n<br>\n";

echo $test->w;

echo "\n<br>\nHello!\n<br>\n";

exit();

Hello!
<br>
111qwerty222
<br>
Hello!
<br>

function t($q){
//print_r($q);
return "sss".$q[1]."ddd";
}


class test {
public $w;

public function __construct(){}
/*
private function t($q){
print_r($q);
return "sss".$q[1]."ddd";
}
*/
public function e(){
$this->w=preg_replace_callback("{(qwerty)}","t","111qwerty222");
}

}


$test=new test();

$test->e();

echo "Hello!\n<br>\n";

echo $test->w;

echo "\n<br>\nHello!\n<br>\n";

exit();

Hello!
<br>
111sssqwertyddd222
<br>
Hello!
<br>