Undefined offset when removing input field that is not the last one - php

Question

I am using this HTML and JQuery code to add input fields:
https://www.sanwebe.com/2013/03/addremove-input-fields-dynamically-with-jquery
with a few changes, my code resembles this, shortened:
$(wrapper).append('<?php echo $this->Form->input("ticket.' +index+ '.startdate"); ?>');
where index is a var that I'm incrementing and decrementing when the add field or remove field buttons are being selected.
The problem is when I remove an element that is not the last one, for example:
I remove text 1, 2, or 3 and then submit it, I get the Undefined offset error, naturally, since the index var of the created elements stays the same, and the server gets
ticket.0.startdate
ticket.2.startdate
ticket.3.startdate
and has no idea where the ticket.1.startdate is.
PHP code:
$festivalticket = $this->Festivaltickets->newEntity();
if ($this->request->is('post')) {
$festivalticket = $this->Festivaltickets->patchEntity($festivalticket, $this->request->data, [
'associated' => [
'Tickets'
]
]);
}
I want to know if there's a way to get past this.
Thank you.

Answer 1

Us an array for your form fields. ticket_startdate[] will dynamically append array elements, so something like:
$(wrapper).append('<?php echo $this->Form->input("ticket_startdate[]"); ?>');
Then just loop through without worrying about the index:
foreach($_POST['ticket_startdate'] as $key => $start_date) {
echo "index $key is $start_date";
}
I can't tell what's going on with the PHP you posted. It looks like a framework so it may handle the array correctly.