我的复选框表单中未定义的偏移量

尽管有"未定义的偏移量"错误，但以下函数工作正常，但我仍然需要调试它。有人可以帮助我发现错误在哪里吗？

这是形式：

$query = "SELECT * FROM application WHERE Shortlist_status = 1 AND Interview_datetime !=  '' AND Email_checked ='' ORDER BY Candidate_id ASC";
$result = mysqli_query($link, $query) or die(mysqli_error($link));
while ($row = mysqli_fetch_array($result)) {
<input type="hidden" name="can_id[]" value=<?php echo $canid ?>>
<input type="hidden" name="job_id[]" value=<?php echo $jobid ?>>
(Some codes)
<input name="email[]" id="id" type="checkbox" value="1">
}

这是表单处理：

foreach ($_POST['can_id'] as $i => $candidate_id) {
$job_id = $_POST['job_id'][$i];
$email = $_POST['email'][$i];
$insertQuery = "UPDATE application SET Email_checked = '$email' WHERE Candidate_id = $candidate_id AND Job_id = $job_id";
$inserted = mysqli_query($link, $insertQuery) or die(mysqli_error($link));
}
if($inserted)
{
    $message = 'Application successfully update <br><a href="interview.php">Manage Candidate</a>';; 
}
else
{
  $message = 'Application failed <br><a href="interview.php">Manage Candidate</a>';
}
echo $message;