Scheduled Tasks - Logging

[Mko]

I've created my own Scheduled Task coded in MySQLi. Although, I'm stumped as to how to make this Scheduled Task Log its actions.

Core Code:

PHP Code:

<?php
error_reporting(E_ALL & ~E_NOTICE & ~8192);
$link = mysqli_init();
mysqli_real_connect($link, 'localhost', 'root', '', 'vbulletin');

$time = time();
// select all banned users who are due to have their ban lifted
$bannedusers = mysqli_query($link, "SELECT * FROM table WHERE time <> 0 AND time < " .$time. "") or print(mysqli_error($link));

$logging = mysqli_fetch_array($bannedusers);

// do we have some results?
if (mysqli_num_rows($bannedusers))
{
    // delete ban records
    mysqli_query($link, "UPDATE table SET time = 0 WHERE timetime <> 0 AND time < " .$time. "") or print(mysqli_error($link));

    // log the cron action
    log_cron_action(implode(', ', $logging['id']), $nextitem, 1);
}

mysqli_free_result($bannedusers);
?>

However, when I execute this Task, I get this error message:
Warning: implode() [function.implode]: Invalid arguments passed in [path]/includes/cron/mycode.php on line 19

Can anyone help me so I can properly Log these actions?

Thanks,
Mark