Ussd with varying questions and responses

Ussd-varying-questions.php

<?php
/**
* Collaborated with http://github.com/pittgikera
*/

$text = $_GET['text'];

//$questions = "How was is it? # Was it enjoyable?# Did you have fun? # Will you come back?";
$questions = "";

//we use array filter to remove indices whose values are empty
$questionsArray = array_filter(explode('#', $questions));

$responseArray = array_filter(explode('*', $text));

if (count($questionsArray) < 1) {
    echo "We don't have questions for you today!";
} else {
    $currentQuestion = null;

    for ($i = 0; $i < count($questionsArray); $i++) {
        if (isset($responseArray[$i + 1])) {
            //question has been answered
        } else {
            //question not answered
            $currentQuestion = $i;
            break;
        }
    }

    if (is_null($currentQuestion)) {
        //if the current question is null, they've answered everything
        echo "You've answered everything";
    } else {
        //show that question now!
        echo $questionsArray[$currentQuestion];
    }

}