Those checkboxes are populated by a MySQL DB, their names are 'checkbox' with the ID for the MySQL field at the end, so : checkbox_, there's some missing, it's normal.<br><br>
	<form name='edit' action='/loop.php' method='post'>
		<input type='checkbox' name='checkbox_1'> ID:1<br>
		<input type='checkbox' name='checkbox_2'> ID:2<br>
		<input type='checkbox' name='checkbox_3'> ID:3<br>
		<input type='checkbox' name='checkbox_7'> ID:7<br>
		<input type='checkbox' name='checkbox_9'> ID:9<br><br>
		<input type='submit' name='submit' value='Submit'>
	</form>