Handling $_POST in Wordpress - wordpress

Question

How can i handle $_POST in wordpress? I am creating a custom "send" button which displays in my plugin's admin panel. When pressing the "send" button, mails have to be send to the subscribers. But how can this be done? How can i handle the custom "send" $_POST button?
I have tried to do it with init, but with no succes:
add_action('manage_nieuwsbrief_posts_custom_column', 'nwsbrf_custom_nieuwsbrief_column', 10, 2);
function nwsbrf_custom_nieuwsbrief_column($column, $post_id) {
global $wpdb;
$getcategories = $wpdb->get_results( $wpdb->prepare("SELECT * FROM wp_nwsbrf_couple INNER JOIN wp_nwsbrf_categories WHERE wp_nwsbrf_couple.category_id = wp_nwsbrf_categories.category_id AND ID = %d", $post_id) );
foreach ($getcategories as $categorie) {
switch ($column) {
case 'cat':
echo $categorie->category_name;
break;
}
}
switch ($column){
case 'send';
echo '<input type="submit" class="button button-secondary button-small" name="send_post" value="Verzenden">';
break;
}
}
add_action('init', 'process_send_post');
function process_send_post(){
if($_POST['send_post']) {
echo 'Postelijk';
}
}

Answer 1

You are looking for the isset() function in PHP:
if(isset($_POST['send_post'])) {
// handle your form
}
In your code, try not to use a switch for single cases, use an if instead, makes your code more readable and compact.
Also you can get the category of a post using the built-in Wordpress function get_the_category($id). No need to execute a DB query yourself