i'm getting an error when using this code for getting my table column names. ``` public function getColumnsNames($table) { $connection = DB::connection(); $connection->getSchemaBuilder(); $table = $connection->getTablePrefix() . $table; $grammar = $connection->getSchemaGrammar(); $results = $connection->select($grammar->compileColumnExists(), array($connection->getDatabaseName(), $table)); return $connection->getPostProcessor()->processColumnListing($results); } ```