Question

I am trying to retrieve exams(sessions) depending on the module the teacher has chosen from the previous drop down menu.

For Example:

Module selected from drop down: CHI2332 (ModuleId) Advanced Database Systems (ModuleName)

Exam(Session) shown in drop down:

AAA (SessionId) 24-04-2012 (SessionDate) 11:00:00 (Session Time)
ARF (SessionId) 13-06-2012 (SessionDate) 14:00:00 (Session Time)
EFT (SessionId) 10-09-2012 (SessionDate) 09:00:00 (Session Time)

It should display the exams above in the drop down menu as these exams match the moduleId chosen from the module dropdown menu and the TeacherId for these exams belong to the Teacher Username logged into to this page.

The problem is that in the Exam drop down menu, it cannot seem to find any exams even though the modules are legitimate for those exams and hence it should display those exams in the drop down menu.

It just outputs this error below in its place:

Sessions: Notice: Undefined variable: sessionHTML in /.../ on line 178

How can I get the exams to appear in the drop down menu when it should do?

Below are the database tables:

Session Table:

SessionId SessionDate SessionTime ModuleId  
AAA       24-04-2012  11:00:00    CHI2332 
ARF       13-06-2012  14:00:00    CHI2332 
EFT       10-09-2012  09:00:00    CHI2332 

Module Table:

ModuleId  ModuleName
CHI2332   Advanced Database Systems

Below is the php/mysqli code:

<?php

         // connect to the database
 include('connect.php');

  /* check connection */
  if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    die();
  }

   $courseid = (isset($_POST['courseid'])) ? $_POST['courseid'] : '';

   ?>

       <h1>DELETING AN ASSESSMENT</h1>

        <form action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>" method="post">
         <p>Course ID: <input type="text" name="courseid" /><input id="courseSubmit" type="submit" value="Submit" name="submit" /></p>      
        </form>


        <?php
if (isset($_POST['submit'])) {

        $query = "
                 SELECT cm.CourseId, cm.ModuleId, 
                 c.CourseName,
                 m.ModuleName
                 FROM Course c
                 INNER JOIN Course_Module cm ON c.CourseId = cm.CourseId
                 JOIN Module m ON cm.ModuleId = m.ModuleId
                 WHERE
                 (c.CourseId = ?)
                 ORDER BY c.CourseName, m.ModuleId
                ";

    $qrystmt=$mysqli->prepare($query);
    // You only need to call bind_param once
    $qrystmt->bind_param("s",$courseid);
    // get result and assign variables (prefix with db)

    $qrystmt->execute(); 

    $qrystmt->bind_result($dbCourseId,$dbModuleId,$dbCourseName,$dbModuleName);

     $qrystmt->store_result();

    $num = $qrystmt->num_rows();

    if($num ==0){
        echo "<p>Sorry, No Course was found with this Course ID '$courseid'</p>";
    } else { 

        $dataArray = array();

 while ( $qrystmt->fetch() ) { 
          // data array
          $dataArray[$dbCourseId]['CourseName'] = $dbCourseName; 
          $dataArray[$dbCourseId]['Modules'][$dbModuleId]['ModuleName'] = $dbModuleName; 
           // session data
          $_SESSION['idcourse'] = $dbCourseId;
          $_SESSION['namecourse'] = $dbCourseName;

    }

     foreach ($dataArray as $courseId => $courseData) {

          $output = ""; 

          $output .= "<p><strong>Course:</strong> " . $courseId .  " - "  . $courseData['CourseName'] . "</p>";

       $moduleHTML = ""; 
       $moduleHTML .= '<select name="module" id="modulesDrop">'.PHP_EOL;
       $moduleHTML .= '<option value="">Please Select</option>'.PHP_EOL;      
            foreach ($courseData['Modules'] as $moduleId => $moduleData) {        

            $moduleHTML .= "<option value='$moduleId'>" . $moduleId . " - " . $moduleData['ModuleName'] ."</option>".PHP_EOL;        
  } 
            }
            $moduleHTML .= '</select>';

      echo $output;

        }


        ?>

         <form action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>" method="post">
         <p>Module: <?php echo $moduleHTML; ?><input id="moduleSubmit" type="submit" value="Submit" name="modulesubmit" /></p>      
        </form> 



        <?php

    }

 if (isset($_POST['modulesubmit'])) {

     var_dump($_POST['modulesDrop']);

            $sessionquery = "
                 SELECT SessionId, SessionDate, SessionTime, ModuleId
                 FROM Session
                 WHERE
                 (ModuleId = ?)
                 ORDER BY SessionDate, SessionTime 
                ";

    $sessionqrystmt=$mysqli->prepare($sessionquery);
    // You only need to call bind_param once
    $sessionqrystmt->bind_param("s",$_POST['modulesDrop']);
    // get result and assign variables (prefix with db)

    $sessionqrystmt->execute(); 

    $sessionqrystmt->bind_result($dbSessionId,$dbSessionDate,$dbSessionTime, $dbModuleId);

     $sessionqrystmt->store_result();

    $sessionnum = $sessionqrystmt->num_rows();   

        $dataArraySession = array();

 while ( $sessionqrystmt->fetch() ) { 

     $dataArraySession[$dbModuleId]['Sessions'][$dbSessionId]['SessionDate'] = $dbSesisonDate['SessionTime'] = $dbSessionTime; 

    }

    foreach ($dataArraySession as $sessionId => $sessionData) {

       $sessionHTML = ""; 
       $sessionHTML .= '<select name="session" id="sessionsDrop">'.PHP_EOL;
       $sessionHTML .= '<option value="">Please Select</option>'.PHP_EOL;           
       $sessionHTML .= "<option value='$sessionId'>" . $sessionId . " - " . $sessionData['SessionDate']. " - " . $sessionData['SessionTime'] ."</option>".PHP_EOL;        
       $sessionHTML .= '</select>';
            }


     if ($sessionnum > 0) {

 ?>

         <form action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>" method="post">
         <p>Sessions: <?php echo $sessionHTML; ?><input id="sessionSubmit" type="submit" value="Submit" name="sesionsubmit" /></p>      
        </form>       

<?php

    }

    else {
   echo "<p>Sorry, You have No Sessions under this Module</p>";
}


}


        ?>

Link to application is here: Application

Answer 1

I see a typo here (line: 111):

$dataArraySession[$dbSessionId]['Sessions']['SessionDate'] = $dbSesisonDate['SessionTime'] = $dbSesisonTime;

You binded parameter is called $dbSessionTime and you’re assigning $dbSesisonTime to your $dataArraySession array. This would cause $dataArraySession not to filled up by any value in your while loop in line 109. Subsequently the foreach loop in line 115 will never be executed and because $sessionHTML is defined inside this loop, will be undefined later on when you use it in line 131

PS: The provided link for your application requires authentication to proceed.

EDIT to provide a code sample in case no data exist for a particular courseId:

Wrap lines 130-132 inside an if statement in order to be sure that the drop-down will be displayed only if some results are found

if ($sessionnum > 0) {
   // display your form
}
else {
   echo "No results found!";
}