[php] Issue with Switch Statement

I have a switch statement I am trying to use in terms of loading individual questions for a test taking website.  I have posted about it before here and I am almost done with everything, but I have one last piece that is throwing me for a loop.

Below is a script that is taking the GET data from the previous question and if there was no previous question, assigning the question data variables a value:

if ($_REQUEST['test_question'] = '' || $_REQUEST['test_question'] = NULL || $_REQUEST['test_question'] = 0) {
    $test_question = 1;
    $_SESSION['current_q'] = 1;

    echo $test_question;

    $get_question = "SELECT test_id, question_primary 
                    FROM create_test_questions 
                    WHERE test_id = '$test_id'
                    ORDER BY question_primary 
                    LIMIT 1";
    $result = mysql_query($get_question);
    $row = mysql_fetch_row($result);

    // Set variable for question id
    $test_question_id   = $row['question_primary'];
    $_SESSION['question_primary'] = $test_question_id;

  } else {
    $test_question      = $_SESSION['current_q']+1;
    $test_question_id   = $_SESSION['question_primary']+1;
    $get_question = "SELECT question_primary 
                    FROM create_test_questions
                    WHERE question_primary = '$test_question_id'
                    LIMIT 1";
    $result = mysql_query($get_question);
    $row = mysql_fetch_row($result);

  };

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Then below is a switch statement that is based on the value of the variable $test_question

switch ($_REQUEST['test_question']){
    case ($_REQUEST['test_question'] = 1):
      
      echo "It is the first question";
      //echo $test_id;
      //echo $test_question;
      
      $get_question = "SELECT test_id, step_number, step_number_sub, step_required, step_description, step_outcome, question_primary 
                      FROM create_test_questions 
                      WHERE test_id = '$test_id'
                      ORDER BY question_primary 
                      LIMIT 1";
      $result = mysql_query($get_question);
      $row = mysql_fetch_row($result);

      // Assign variables to populate question
      $test_id            = $row['0'];
      $step_number        = $row['1'];
      $step_number_sub    = $row['2'];
      $step_required      = $row['3'];
      $step_description   = $row['4'];
      $step_outcome       = $row['5'];
      $test_question_id   = $row['6'];


      // Prepare variables for grabbing next question
      $test_question = $_REQUEST['test_question'] + 1;
      $_SESSION['current_q'] = $test_question;

      $test_question_id = $test_question_id + 1;
      $_SESSION['question_primary'] = $test_question_id;
      break;

    case ($_REQUEST['test_question'] > 1 && $_REQUEST['test_question'] < $q):
      
      echo "It is a middle question";
      echo $test_question;
      // Get the next question
      $get_question = "SELECT test_id, step_number, step_number_sub, step_required, step_description, step_outcome, question_primary 
                      FROM create_test_questions
                      WHERE question_primary = $test_question_id
                      LIMIT 1";
      $result = mysql_query($get_question);
      $row = mysql_fetch_row($result);

      // Assign variables to populate question
      $test_id              = $row['test_id'];
      $step_number          = $row['step_number'];
      $step_number_sub      = $row['step_number_sub'];
      $step_required        = $row['step_required'];
      $step_description     = $row['step_description'];
      $step_outcome         = $row['step_outcome'];
      $test_question_id     = $row['question_primary'];


      // Prepare variables for grabbing next question
      $test_question = $_REQUEST['test_question'] + 1;
      $_SESSION['current_q'] = $test_question;

      $test_question_id = $test_question_id + 1;
      $_SESSION['question_primary'] = $test_question_id;

      // Load previous test data to the database
      if ($_REQUEST['step_number'] = NULL) {
        $load_result = "INSERT INTO `create_test_results` test_id, res_step_number, res_step_sub_number, res_step_outcome, res_step_notes, rest_test_taker) 
                      VALUES ('$_SESSION[test_id]','$_REQUEST[step_number]','$_REQUEST[step_sub_number]','$_REQUEST[step_outcome]','$_REQUEST[step_notes]','$_REQUEST[test_taker]')";
        $load = mysql_query($load_result);
      }
      break;

    case ($_REQUEST['test_question'] = $q):
      
      echo "It is a last question";

      // Load previous test data to the database
      $load_result = "INSERT INTO `create_test_results` test_id, res_step_number, res_step_sub_number, res_step_outcome, res_step_notes, rest_test_taker) 
      VALUES ('$_SESSION[test_id]','$_REQUEST[step_number]','$_REQUEST[step_sub_number]','$_REQUEST[step_outcome]','$_REQUEST[step_notes]','$_REQUEST[test_taker]')";
      $load = mysql_query($load_result);

      // Hide the form and then complete the case
      ?>

      <script type="text/javascript">$('#form').hide()</script>

      <?php
      echo "<h3>You have completed the test and your results have been submitted. Thank you for your time.</h3>";
      echo "<p>If you would like to take another test, please click here to view the list of available tests</p>";
      $_SESSION['question_primary'] = '';
      break;

    case ($test_question > $q || $test_question < 1):

      echo "It is the error";
      $_SESSION['current_q']      = 1;
      $_SESSION['question_primary']   = 1;
      echo "Error submitting test. Conteact Webmaster";
      break;
    
    default:
      
      echo "It is the default";
      $get_question = "SELECT test_id, step_number, step_number_sub, step_required, step_description, step_outcome, question_primary 
      FROM create_test_questions 
      WHERE question_primary = '$test_id'
      ORDER BY question_primary 
      LIMIT 1";
      $result = mysql_query($get_question);
      $row = mysql_fetch_row($result);

      // Assign variables to populate question
      $test_id            = $row['test_id'];
      $step_number        = $row['step_number'];
      $step_number_sub    = $row['step_number_sub'];
      $step_required      = $row['step_required'];
      $step_description   = $row['step_description'];
      $step_outcome       = $row['step_outcome'];
      $test_question_id   = $row['question_primary'];


      // Prepare variables for grabbing next question
      $test_question = $_REQUEST['test_question'] + 1;
      $_SESSION['current_q'] = $test_question;

      $test_question_id = $test_question_id + 1;
      $_SESSION['question_primary'] = $test_question_id;
      break;
  };

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I am able to get the first question to show, but it never goes to the next question when I click the next button.

Thanks for any help you can offer and please let me know if you need any other information.  Thanks again!