<form>
	<select name="cat[1]">
		<option value="food">FOOD</option>
		<option value ="electronics">ELECTRONICS</option>
	</select>
	<select name="subcat[1][]">
		<option value="1">Bakes & Nuts</option>
		<option value="2">Drinks</option>
	</select>
	<input type="file" name="catimage[2]">
	<select name="cat[2]">
		<option value="food">FOOD</option>
		<option value ="electronics">ELECTRONICS</option>
	</select>

	<select name="subcat[2][]">
		<option value="1">Bakes & Nuts</option>
		<option value="2">Drinks</option>
	</select>
	<input type="file" name="catimage[2]">

	<input type="submit" name="submit" value="submit">
</form>

<?php
foreach ($_POST['cat'] as $key => $value) {
	// sanatize/validate your inputs
	$cat = $value;
	$subcat = implode(',', $_POST['subcat'][$key]);
	$file = $_FILES['catimage']
	// insert
}
?>