CodeIgniter Multiple Row Update - php

Question

I'm having a problem with a project of mine. I have read around and have no idea on what to do any more. This is a Codeigniter todo list project for our small office. I have made the displaying the contents of the database part already however I'm stumped on the updating part. On the view part, there's a todo list with checkboxes. If they are completed with the task, then they check the box and then put in the date when they did it and their initials. So they can check a lot of tasks and put dates and initials and I'm having a problem updating them in one time. I'm stumped. Please help. Thanks!
Controller
public function update_tasks() {
$this->load->model('model_members');
$post=$this->input->post();
$this->model_memberdashboard->reset_tasks($this->session->userdata('UserID')); // resets completion status of all tasks since checkboxes that are not checked doesn't do Post
foreach ($post['checkbox'] as $row){
$newData = array(
'completed'=> 1
);
$this->model_members->update_tasks($newData,$row);
}
$this->index();
Model
public function update_tasks($data,$id) {
$this->db->update("mastertaskslist",$data,['id' => $id]);
}
View <- Im using bootstrap so its a bit long
foreach ($allowedTasklist_1 as $row) {
echo '<li class="ui-state-default clearfix">';
echo '<div class=row>';
echo '<div class="col-sm-1">';
$checkbox=array(
'name' => 'checkbox[]',
'id' => 'checkbox[]',
'type' => 'checkbox',
'value' => $row->id,
'checked' => $row->completed,
);
if ($row->completed=="False"){
unset($checkbox['checked']);
}
echo form_checkbox($checkbox);
echo '</div>';
echo '<div class="col-sm-1">';
echo '<label>'.$num.'.'.'</label>';
echo '</div>';
echo '<div class="col-sm-10">';
echo '<div class="row">';
echo '<div class="col-sm-12">';
echo '<p>'.$row->taskTitle.'</p>';
echo '</div>';
echo '</div>';
echo '<div class="row">';
echo '<div class="col-sm-8">';
if ($row->lastUpdate=='0000-00-00'){
$currDate=NULL;
} else {
$currDate=date('m/d/Y', strtotime($row->lastUpdate));
}
$date=array(
'type' => 'text',
'class' => 'datepicker',
'name' => 'date['.$row->id.']',
'id' => 'date['.$row->id.']',
'value' => $currDate,
'placeholder' => 'mm/dd/yyyy',
'size' => '15'
);
echo form_input($date);
echo '</div>';
echo '<div class="col-sm-4">';
$initials=array(
'name' => 'initials['.$row->id.']',
'id' => 'initials[]',
'value' => $row->initials,
'maxlength' => '100',
'size' => '3',
);
echo form_input($initials);
echo '</div>';
echo '</div>';
echo '</div>';
echo '</div>';
$num++;
echo '</li>';
}