How can I pass a selected option from a dropdown menu to a new page in PHP?

Question

This is my html for the search bar and dropdown.

<form action='seniorProjectLanding.php' method='POST' class='form-group'>
            <div class="form-horizontal" align="center">
              <input type="text" name="searchResults" 
                class="form-control" 
                placeholder="Search"
                style="width:80%; max-width:80%; display:inline-block"/>

              <button type="submit" 
                class="btn btn-primary"
                name="submit"
                style="margin-left:-8px; margin-top:-2px; min-height:36px;">
                <i class="glyphicon glyphicon-search"></i>
              </button>
            </div>

            <div class="row" align="center">
              <div class="form-group" style="width: 50%" align="center">
                <select id="dropdownForm" name="sortDropdown" class="form-control">
                  <option value="Name">Item Name</option>;
                  <option value="LocationID">Location</option>;
                  <option value="CategoryID">Category</option>;
                  <option value="Quantity">Quantity</option>;
                  <option value="LastQuantityUpdate">Most Recently Updated</option>;
                </select>
              </div>
            </div>
          </form>

And this is the PHP.

if (isset($_POST["submit"])) {

  $searchResults = $_POST["searchResults"];
  $dropdownSelection = $_GET["dropdownForm"];

  if ($searchResults !== "") {
    header("Location: test2.php?sortBy=".$dropdownSelection."&searchResults=".$searchResults);
  }
  else {
    header("Location: test2.php?sortBy=".$dropdownSelection);
  }

}

I have gotten this to work using the input from a search box, but cannot seem to get it to work with this dropdown menu and its selected option values.

Answer 1

Try adding a submit button...

Defines a submit button (for submitting the form).

<input type="submit"> defines a button for submitting the form data to a form-handler.

The form-handler is typically a server page with a script for processing input data.

The form-handler is specified in the form's action attribute.

Try using:

<form action="test1.php" method="POST" class="form-group">
        <div class="row" align="center">
          <div class="form-group" style="width: 50%" align="center">
            <select id="dropdownForm" name="sortDropdown" class="form-control">
              <option value="Name">Item Name</option>;
              <option value="LocationID">Location</option>;
              <option value="CategoryID">Category</option>;
              <option value="Quantity">Quantity</option>;
              <option value="LastQuantityUpdate">Most Recently Updated</option>;
            </select>
        </div>
      </div>
      <input type="submit" name="submit" value="Submit" />
      </form>

Documentation: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/submit

Answer 2

If you're wanting to add parameters to the query string, you want to use a form with a GET method instead. Then when you submit the form, its data will be added to the query string (ie for filtering/sorting search results):

<form action="test1.php" method="GET">
  <select name="sort_by">
    <option value="name">Name</option>
    <!-- and so on -->
  </select>
  <button type="submit">Submit</button>
</form>

This will submit to test1.php?sort_by=name if the name option is selected.

You can add more fields as required. You'd also then access the values using $_GET instead:

$sort_by = $_GET['sort_by'];

Answer 3

You are posting but are trying to access a get variable. Also, you are using the control id dropdownForm and not the name sortDropdown :

$dropdownSelection = $_GET["dropdownForm"];

Should be:

$dropdownSelection = $_POST["sortDropdown"];

Using error reporting:

error_reporting(E_ALL);
ini_set('display_errors', '1');

Would have given you this:

Notice: Undefined index: dropdownForm in /path/to/file.php on line X