Add unique identifier to first iteration in PHP for loop - php

Question

I am using a for loop on my client's website to insert purchased ticket information into a database. The loop is working correctly, but the client has requested the option to attach a unique identifier to the first entry every time the for loop is run. This identifier would be used to highlight the primary ticket owner when the tickets are printed. I have included the current for loop below for reference. Any ideas on how to achieve this? Thank you.
$threepack = '';
$i = '';
for($i = 0; $i < $tickets; $i++)
{
$firstname = 'firstname'.$threepack;
$lastname = 'lastname'.$threepack;
$address = 'address'.$threepack;
$city = 'city'.$threepack;
$postal = 'postal'.$threepack;
$phone = 'phone'.$threepack;
$altphone = 'altphone'.$threepack;
$sec_firstname = 'sec_firstname'.$threepack;
$sec_lastname = 'sec_lastname'.$threepack;
$email = 'email'.$threepack;
$table->firstname = $data->$firstname;
$table->lastname = $data->$lastname;
$table->address = $data->$address;
$table->city = $data->$city;
$table->postal = $data->$postal;
$table->phone = $data->$phone;
$table->altphone = $data->$altphone;
$table->sec_firstname = $data->$sec_firstname;
$table->sec_lastname = $data->$sec_lastname;
$table->email = $data->$email;
$table->id = 0;
$table->order_total = $data->total;
$table->store();
if($data->tickets == '-1')
{
if($threepack == 2)
{
$threepack = 3;
} else {
$threepack = 2;
}
}
// 8 Fields
if($data->tickets == '5')
{
if ($threepack == '') {
$threepack = 2;
} else {
$threepack += 1;
}
}
}

Answer 1

for ($i = 0; $i < $tickets; $i++) {
// ...
if ($i == 0)
$table->highlightme = 1;
// ...
$table->store();
// ...
}