You are not passing JS variable value to PHP via ajax

Question

Javascript

$('#save-update').data('eventId', info.event.id);

$('#delete-update').click(function (info) {
        info.preventDefault();        
        let eventID = $('#save-update').data('eventId');        
        $.ajax({
            type: 'POST',
            url: 'php/delete-events.php',             
            data: eventID,       
            contentType: false,
            processData: false,
            success: function(response) {
                location.reload();                       
            }
        })
    });

PHP

$id = $_POST['eventID'];

The id value for the PHP file is not coming. Notice: Undefined index: eventID

Answer 1

You need to send the variable in a JS object

$('#delete-update').click(function (info) {
        info.preventDefault();        
        let eventID = $('#save-update').data('eventId');        
        $.ajax({
            type: 'POST',
            url: 'php/delete-events.php',             
            data: {eventID:eventID},       // Alterado aqui
            contentType: false,
            processData: false,
            success: function(response) {
                location.reload();                       
            }
        })
    });

Explaining

           ⬐ ex. $_POST['eventID']
data: { eventID : eventID },
              Valor ⬏