Interpolated String Issue

make_path.php

<?php       
          // I want this to work but I don't want to split and rejoin for operators
          if(strpos($data, '.') !== false){
                $data = self::makePath($data);
                // client->client_name
                return self::$order->{$data};
          }
          
          // This Works
          if(strpos($data, '.') !== false){
                $a ='client';
                $b = 'client_name';
                return self::$order->{$a}->{$b};
          }