PHP Object Variable variables name?

Actually you need to take the variable outside the string like this in order to those solutions to work: $var="field_question_".$i;

$entity_object->$var;

Or

$entity_object->{"field_question_".$i}

First of all, arrays are more suitable for what you want to do.

The answer to you question: print $entity_object->{"field_question_$i"};

This should work:

$var="field_question_$i";
$entity_object->$var;