php string to array

$str = "array ( 'k1'=>'v1', 'k2'=>array ( 'k21'=>'v21', 'k22'=>'v22'))";
eval('$arr='.$str.';');//['_id' => new MongoDB\BSON\ObjectID, "data" =>["k" => "v","k2" => "v2"],"v"=>1];
print_r(var_dump($arr));