Codeigniter Error Duplicate entry '' for key 'PRIMARY' when looping insert statement

I'm setting this function up in codeigniter to run as a cron job and log all users out at X time. I've used this code succesfully when selecting one user and logging that user out, but when adding the foreach, I get the following error:

Error Number: 1062

Duplicate entry '3858' for key 'PRIMARY'

INSERT INTO `time` (`id`, `projectid`, `phaseid`, `firstname`, `timest`, `status`, `activityid`, `todate`, `remark`, `time`, `workperiod`, `activitydate`, `entrydate`) VALUES ('3858', '212132 Unilever Nigeria  10000L Toothpaste Storage Tanks x 2', '1', 'BONGANI', '1347610976', '1', '1', '1', '1', 3335907, 'nothing', '2012-09-14 10:22:56', '2012-10-23 01:01:23')

Filename: C:\xampp\htdocs\projectfiles\protime\v2\system\database\DB_driver.php

Line Number: 330

This is the code for the model:

function punch_out() {
    $this -> load -> database();
    $this -> load -> helper('date');
    //get people
    $this -> db -> select('*');
    $this -> db -> from('person');
    $this -> db -> order_by("department", "asc");
    $this -> db -> order_by("userid", "asc");
    $query = $this -> db -> get();
    foreach ($query->result_array() as $row) {
        $people[] = $row;

    }

    foreach ($people as $row) :

    $this -> db -> from('punch');
    $this -> db -> where('firstname', $row['firstname']);
    $this -> db -> order_by("id", "desc");
    $this -> db -> limit(1);
    $query = $this -> db -> get();
    foreach ($query->result_array() as $row) {
        $data = $row;
    }

    $data['workperiod'] = 'nothing';

    $current_time = getdate();

    if ($current_time['wday'] > '0' && $current_time['wday'] < '5') {
        if ($current_time['hours'] > '7' && $current_time['hours'] < '12') {
            $data['workperiod'] = 'stda';
        } else if ($current_time['0'] > strtotime('4:16am') && $current_time < strtotime('11:59pm')) {
            $data['workperiod'] = 'ota';
        }
    } else if ($current_time['wday'] == '5') {
        if ($current_time['0'] > strtotime('7:00am') && $current_time < strtotime('11:59am')) {
            $data['workperiod'] = 'stdb';
        } else if ($current_time['0'] > strtotime('1:01am') && $current_time < strtotime('11:59pm')) {
            $data['workperiod'] = 'otb';
        }
    } else if ($current_time['wday'] == '6') {
        $data['workperiod'] = 'otc';
    } else if ($current_time['wday'] == '0') {
        $data['workperiod'] = 'dtc';
    }

    if ($data['status'] == 1) {
        //MAKE TIME
        $now = time();
        $data['time'] = elapsed_time($data['timest'], $now);
        $data['entrydate'] = timestamp_to_mysqldatetime($now);
        $data['activitydate'] = timestamp_to_mysqldatetime($data['timest']);
        $this -> db -> insert('time', $data);
    }

    endforeach;
}

If you are trying to update the data (time,entrydate,activitydate) of the same id you are inserting, i think it is much better if you put only the data to a new array something like:

if ($data['status'] == 1) {
    //MAKE TIME
    $now = time();
    $newdata['time'] = elapsed_time($data['timest'], $now);
    $newdata['entrydate'] = timestamp_to_mysqldatetime($now);
    $newdata['activitydate'] = timestamp_to_mysqldatetime($data['timest']);
    $this -> db -> where('id',$data['id']);
    $this -> db -> update('time', $newdata);
}

Or if you are trying to insert a new record to your database just change the array name you are trying to insert:

if ($data['status'] == 1) {
    //MAKE TIME
    $now = time();
    $newdata['time'] = elapsed_time($data['timest'], $now);
    $newdata['entrydate'] = timestamp_to_mysqldatetime($now);
    $newdata['activitydate'] = timestamp_to_mysqldatetime($data['timest']);
    $this -> db -> insert('time', $newdata);
}

In this way of coding, this might avoid more error in the future and might save time.

Cheers!