MySQL trigger keeps adding two rows for every update - php

Question

I am trying to update a 'ticketHistory' table after every update of my 'tickets' table. I have the following trigger set up to run whenever my 'tickets' table is updated (usually when a field is edited):
TRIGGER `ticket_edit` AFTER UPDATE ON `tickets` FOR EACH ROW INSERT INTO ticketHistory
(ticketId, action, originator, assigned, date)
VALUES
(NEW.ticketId, "Edited", NEW.userId, NEW.assigned, NEW.lastUpdated);
Whenever an update is done in my app, the field being edited is updated, as well as the 'lastUpdated' time. I think because two fields are being updated, it is running the trigger twice, resulting in two identical rows being inserted into my 'ticketHistory' table. I only want one row inserted.
Is there a way to limit it to just one row being inserted? Any help is greatly appreciated!
EDIT
All database inserts and updates are being done using CodeIgniter's ActiveRecord.
My model:
public function editTicket($ticket)
{
$q = $this->db->where('ticketId', $ticket['ticketId']);
$q = $this->db->update('tickets', $ticket);
$results = $this->db->affected_rows();
}
My Controller:
public function edit_ticket()
{
$ticketId = $this->uri->segment(3);
$description = str_replace("\n", "\r", $this->input->post('description'));
$ticket = array(
'ticketId' => $ticketId,
'headline' => $this->input->post('headline'),
'description' => $description,
'priority' => $this->input->post('priority'),
'category' => $this->input->post('category'),
'lastUpdated' => date("Y-m-d H:i:s", time())
);
$this->tickets->editTicket($ticket);
}

Answer 1

public function editTicket($ticket)
{
$q = $this->db->where('ticketId', $ticket['ticketId']);
echo "I am here again<br/>";
$q = $this->db->update('tickets', $ticket);
$results = $this->db->affected_rows();
}

Answer 2

I'm not sure why that's adding 2 different rows, but you could just make a primary key field and your DBMS wouldn't allow the duplicate.
Hope this helps!

Answer 3

So, as a solution, I modified my trigger as such:
TRIGGER `ticket_edit` AFTER UPDATE ON `tickets`
FOR EACH ROW
IF NEW.headline <> OLD.headline || NEW.description <> OLD.description || NEW.priority <> OLD.priority
THEN
INSERT INTO ticketHistory
(ticketId, action, originator, assigned, date)
VALUES
(NEW.ticketId, "Edited", NEW.userId, NEW.assigned, NEW.lastUpdated);
END IF
By adding the conditionals, I think it only activated the trigger once, resulting in only one row being inserted.
Hope this helps someone!