Question

In my code below I have 2 drop down menus. One is a “Course” drop down menu and the other is a “Modules” drop down menu:

Below is the code:

   <?php

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

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

    $sql = "SELECT CourseId, CourseName FROM Course ORDER BY CourseId"; 

    $sqlstmt=$mysqli->prepare($sql);

    $sqlstmt->execute(); 

    $sqlstmt->bind_result($dbCourseId, $dbCourseName);

    $courses = array(); // easier if you don't use generic names for data 

    $courseHTML = "";  
    $courseHTML .= '<select name="courses" id="coursesDrop" onchange="getModules();">'.PHP_EOL; 
    $courseHTML .= '<option value="">Please Select</option>'.PHP_EOL;  

    while($sqlstmt->fetch()) 
    { 
    $course = $dbCourseId;
    $coursename = $dbCourseName; 
    $courseHTML .= "<option value='".$course."'>" . $course . " - " . $coursename . "</option>".PHP_EOL;  
    } 

    $courseHTML .= '</select>'; 

    $moduleHTML = "";  
    $moduleHTML .= '<select name="modules" id="modulesDrop">'.PHP_EOL; 
    $moduleHTML .= '<option value="">Please Select</option>'.PHP_EOL;  
    $moduleHTML .= '</select>'; 


    include('noscript.php');

    ?>

    <script type="text/javascript">

    function getModules() { 
    var course = jQuery("#coursesDrop").val(); 
    jQuery('#modulesDrop').empty(); 
    jQuery('#modulesDrop').html('<option value="">Please Select</option>'); 
    jQuery.ajax({ 
    type: "post", 
    url:  "module.php", 
    data: { course:course }, 
    success: function(response){ 
    jQuery('#modulesDrop').append(response); 
    } 
    }); 


    }

    </script> 

<h1>EDIT AN ASSESSMENT'S DATE/START TIME</h1>    

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

<?php

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

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

$sessionqrystmt=$mysqli->prepare($sessionquery);
// You only need to call bind_param once
$sessionqrystmt->bind_param("si",$moduleId,$userid);
// get result and assign variables (prefix with db)

$sessionqrystmt->execute(); 

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

$sessionqrystmt->store_result();

$sessionnum = $sessionqrystmt->num_rows();   

if($sessionnum ==0){
echo "<p>Sorry, You have No Sessions under this Module</p>";

module.php where it displays “Module” drop down menu:

 <?php

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

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


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

    $sql = "
    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.CourseId, m.ModuleId
    "; 

     $sqlstmt=$mysqli->prepare($sql);

     $sqlstmt->bind_param("s",$course);

     $sqlstmt->execute(); 

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


    $moduleHTML  = "";  

     while($sqlstmt->fetch()) { 
        $moduleHTML .= "<option value='$dbModuleId'>" . $dbModuleId . " - " . $dbModuleName . "</option>".PHP_EOL;   
    } 


    echo $moduleHTML; 

     $sqlstmt->execute(); 


    ?>

Now if you look at the bottom of the code, what happens is that it performs a query after the user has submitted the “Course” and “Module” drop down menus. if it doesn’t find a session related with that module then it echos "Sorry, You have No Sessions under this Module".

But what my question is that I do not want this echo to be displayed if the user has not selected a “Course” and “Module” from their drop down menus or if the user has selected a course from the “Course” drop down menu but has not selected a module from the “Module” drop down menu.

Below is the echo’s I wanted for each situation:

1. If user has not selected a course and a module: echo "Please Select a Course and Module";
2. If user has selected a course but not a module: echo "Please Select a Module";
3. If user has selected a course and module but no sessions appear: echo "Sorry, You have No Sessions under this Module";

List 3 from above at the moment works but how can I get list 1 and 2 to work by only displaying their echo’s and no other echo?

UPDATE:

Javascript code where it validates drop down menus:

     function validation() {

                var isDataValid = true;

                var moduleTextO = document.getElementById("coursesDrop");
            var courseTextO = document.getElementById("modulesDrop");

            var errModuleMsgO = document.getElementById("moduleAlert");

  if (courseTextO.value == "" && moduleTextO.value == ""){
          errModuleMsgO.innerHTML = "Please Select a Course and Module";
          isDataValid = false;
  } else if (courseTextO.value == ""){
          errModuleMsgO.innerHTML = "Please Select a Course";
          isDataValid = false;      
  }else  if (moduleTextO.value == ""){
          errModuleMsgO.innerHTML = "Please Select a Module";
          isDataValid = false;    
    }else{
                errModuleMsgO.innerHTML = ""; 
        }

        return isDataValid;

        }

Below is HTML code:

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

Answer 1

Change your form tag

<form action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>" method="post">

to

<form action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>" method="post" onsubmit="return validation();">

It’s a good idea to validate on serverside too, just add a little code in your existing PHP if you want to check values on serverside:

<?php

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

if(empty($_POST['courses']) && empty($_POST['modules'])) {
   echo 'Please Select a Course and Module';
} elseif(empty($_POST['courses'])) {
   echo 'Please Select a Course';
} elseif(empty($_POST['modules'])) {
   echo 'Please Select a module';
} else {

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

$sessionqrystmt=$mysqli->prepare($sessionquery);
// You only need to call bind_param once
$sessionqrystmt->bind_param("si",$moduleId,$userid);
// get result and assign variables (prefix with db)

$sessionqrystmt->execute(); 

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

$sessionqrystmt->store_result();

$sessionnum = $sessionqrystmt->num_rows();   

if($sessionnum ==0){
echo "<p>Sorry, You have No Sessions under this Module</p>";

}