`The article for M. {{user.lastname}} is {{user.article.title}}`.

`The article for M. Doe is MyAmazingArticle`

public function preview( $user)
{
    return preg_replace_callback('~{{(.*?)}}~', //Get everything inside double brackets
        function( $key ) use ( $user ) //Use anonymous function to pass additionals variables
        {

            $parts = explode('.' , $key[1]); //Create array

            switch ( count($parts) )
            {
                case '2': $data = ${$parts[0]}->{$parts[1]} ?? 'NULL'; break;

                case '3': $data = ${$parts[0]}->{$parts[1]}->{$parts[2]} ?? 'NULL'; break;

                case '4': $data = ${$parts[0]}->{$parts[1]}->{$parts[2]}->{$parts[3]} ?? 'NULL'; break;

                case '5': $data = ${$parts[0]}->{$parts[1]}->{$parts[2]}->{$parts[3]}->{$parts[4]} ?? 'NULL'; break;

                default: $data = 'NULL'; break;
            }

            return $data;
        },
        htmlspecialchars_decode( $this->html) );
}