How do I output Multi-Dimentional array from db table?

Volitics

Can anyone tell me how to make a multidimentional array?

I'm trying to keep the Main Categories and the Sub-Categories in the same table. The table structure is like this:

id (auto_increments)
MainCategory (has Autos, Advertising, etc.)
SubCategory (has Newspaper, Magazine Ads, Billboards, Repair Garages, etc.)

What I am doing is trying to output select boxes on a web site like so:

id	MainCategory	SubCategory
1	Advertising	Newspaper Ads
2	Advertising	Newspaper Ads
3	Advertising	Newspaper Ads
4	Autos		Repair Garages
5	Autos      	New Cars
6	Autos		Used Cars

// I get the main category from the db and remove the extra ones.
$Headings = array_unique(MainCategory);

// This is where I'm stuck.
// I need to output each <select name=".. just one - which I can do. But then I need to extract the id and the SubCategory and insert  them into the <option value="... menus.
// What I need to do (I think) is insert the three sub-arrays into each element of the big array (Advertising, Autos, etc.)
<select name="Advertising[]" multiple size="7">
<option value="1">Newspaper Ads</option>
<option value="2">Magazine Ads</option>
<option value="3">Billboards</option>
</select>

<select name="Autos[]" multiple size="7">
<option value="4">Repair Garages</option>
<option value="5">New Cars</option>
<option value="6">Used Cars</option>
</select>

Thanks.

konsu

hello,

although you mentioned the structure of your table, it is still not clear to me how the data are stored. are MainCategory and SubCategory fields of type string? could you post a few rows from your table?

Volitics

konsu;

Thanks for responding. The MainCategory and the SubCategory columns are strings.

I'm starting to get it figured out. I'm not sure that a multi-dimentional array is what I need.

What I'm doing is putting it in a nested loop.

The big loop outputs the main category. The inside loop outputs or extracts the sub categories and the id's.

Here's what it looks like:

$Result = mysql_query ("SELECT Abbr FROM Industry");
while ($Row = mysql_fetch_array ($Result)){
	$Abbr[] = trim($Row['Abbr']);
}
$Headings = array_unique($Abbr);

foreach ($Headings as $SingleHeading){
$Result = mysql_query ("SELECT category_id, BroadCategory, SubCategory FROM Industry WHERE Abbr = '$SingleHeading'");
	while ($Row = mysql_fetch_array ($Result)){
		$SubCategory[] = "<option value=\"".trim($Row['category_id'])."\">".trim($Row['SubCategory'])."</option>\n";
	}

$ItemBox[] = "<tr><td><select name=\"".$SingleHeading."\" multiple size=\"7\" width=\"250\">".$SubCategory."</select></td></tr>\n";
unset($SubCategory);
}

I think it's going to work but I'm not sure.

konsu

there is no need for two separate select queries and two separate loops. i would query the database just once, get a list of rows SORTED by first, MainCategory field and then by SubCategory. then i would loop through the resultset and use the fact that the main categories in the resultset are grouped because the resultset is sorted. so when you detect that the main category in the current loop iteration (in the current row) is not the same as in the previous row, it is time to start a new "select" tag. i hope this helps.