[eluser]Noahs Arkive[/eluser]
I think what you want is something like:
<input type="checkbox" name="day[]" value="monday" id="monday" /><label for="monday"> Monday</label><br />
<input type="checkbox" name="day" value="tuesday" id="tuesday" /><label for="tuesday"> Tuesday</label><br />
<input type="checkbox" name="day" value="wednesday" id="wednesday" /><label for="wednesday"> Wednesday</label><br />
<input type="checkbox" name="day" value="thursday" id="thursday" /><label for="thursday"> Thursday</label><br />
<input type="checkbox" name="day" value="friday" id="friday" /><label for="friday"> Friday</label><br />
If monday and wednesday are checked (no need for an array, 'day' will return a comma-delimeted list or does not exist):
// Use the Input class; it's automatically loaded by System
$cked=$this->input->post("day");
echo $cked; // 'monday,wednesday' or FALSE is nothing is clicked
