Submitting form to admin-post.php Wordpress

Question

I've been trying to get a basic plugin to work and I have followed what seems to be the flow to get the form to post to admin-post.php.

However, I only seem to get the white screen of death upon form submission.

This is my main plugin file

<?php 
/**
 * Plugin Name: Test form
 */

function wp_meetings_menu(){
    add_menu_page('Meetings', 'Meetings', 'manage_options', 'wp_meetings', 'wp_meetings_form');
}

add_action('admin_menu', 'wp_meetings_menu');

function wp_meetings_form() {
    ?>
    <div class="wrap">
        <h2>Meetings</h2>
        <form method="post" action="<?php echo admin_url('admin-post.php'); ?>" enctype="multipart/form-data">
            <label>Date and Time:</label>
            <input type="datetime-local" name="datetime"><br><br>
            <label>Drop Down 1:</label>
            <select name="dropdown1">
                <option value="option1">Option 1</option>
                <option value="option2">Option 2</option>
                <option value="option3">Option 3</option>
            </select><br><br>
            <label>Drop Down 2:</label>
            <select name="dropdown2">
                <option value="option1">Option 1</option>
                <option value="option2">Option 2</option>
                <option value="option3">Option 3</option>
            </select><br><br>
            <label>Drop Down 3:</label>
            <select name="dropdown3">
                <option value="option1">Option 1</option>
                <option value="option2">Option 2</option>
                <option value="option3">Option 3</option>
            </select><br><br>
            <label>PDF File:</label>
            <input type="file" name="pdf_file"><br><br>
            <input type="submit" name="submit" value="Submit">
            <input type="hidden" name="action" value="wp_meetings_submit" />
        </form>
    </div>
    <?php
}

?>

and this is the code in the functions.php file that is supposed to handle that submission to admin-post.php

// Handle form submission and database insertion
add_action( 'admin_post_wp_meetings_submit', 'wp_meetings_submit' );
add_action( 'admin_post_nopriv_wp_meetings_submit', 'wp_meetings_submit' );

function wp_meetings_submit(){
    global $wpdb;
    if(isset($_POST['submit'])){
        $datetime = $_POST['datetime'];
        $dropdown1 = $_POST['dropdown1'];
        $dropdown2 = $_POST['dropdown2'];
        $dropdown3 = $_POST['dropdown3'];
        $pdf_file = $_FILES['pdf_file']['name'];
        $upload_dir = wp_upload_dir();
        $pdf_path = $upload_dir['path'] . '/' . $pdf_file;
        move_uploaded_file($_FILES['pdf_file']['tmp_name'], $pdf_path);
        $wpdb->insert(
            'wp_meetings',
            array(
                'datetime' => $datetime,
                'dropdown1' => $dropdown1,
                'dropdown2' => $dropdown2,
                'dropdown3' => $dropdown3,
                'pdf_file' => $pdf_file
            ),
            array(
                '%s',
                '%s',
                '%s',
                '%s',
                '%s'
            )
        );
    }
}

All I get when posting the form is a white screen of death with a blank die message error box.

I configured the WP_DEBUG to be true, but when recreating the error again, no debug log is generated.

I was wondering what is the correct and full way of accomplishing this?

Answer 1

First thank you to @TomJNowell for helping me to figure this out. There was a few misleading assumptions I made that had me making this harder than it needed to be.

There's no need to post to admin-post, keeping the action blank to submit to the current page is perfectly fine.

I don't seem to need to add the url parameter that wordpress automatically adds either.

The url parameters do not get placed in the url bar, leading me to believe it was not getting posted. (Assumption) Upon adding this to the file:

<?php
    if(isset($_POST['submit'])){
        echo "Submit detected!";
        print_r($_POST);
    }
?>

I was able to see that the input data was very much getting posted and I just need to take it from this point.

Thanks again !