Calvin,the best way to test this it to output the values of the datarow corresponding to the check box then see if it is "outputting" (for lack of a better word!!) all the values of the selected checkboxes. Deleting the data from tables without actually testing first if it works will make you refill the tables again, quite tedious, as I could imagine!
Scenario.
1. Say you have read/queried data from a table thru a query.
2. The query returns 6 rows and these are displayed in whatever GUI you are using.
3. From the display, your delete/deletion criteria matches rows no# 3, 4 and 5 in the query results displayed (in 2 abovee)
4. Select the checkboxes matching them, i.e. check boxes at index 2, 3 and 4
5. Display these values first i.e data in the row of the selected checkbox
The trick is, out of the values returned from the query in 2. above, each data row has its primary key (or any unique identifier)
Match the specific UIDs of the displayed data to the selected check box index in a temp store e.g.
LOOP starts here
if chechbox is selected
then dispay_corresponding_value_of_actual_data //not value of checkbox index
array_of_UIDs[$index]=getSelectedCheckBoxindexValue[$checkboxindex]; // find some way of matching these values!!
//e.g in a string array
esle
display nothing or do nothing!
From this analogy, your $del_id = $checkbox[$i]; is wrong. :-)
You could say,
LOOP $del_id = $array_of_UIDs[count_of_selected_checkboxes]; //this is got from the array_of_UIDs[] size
then obviously delete, $sql = "update products set product_price = '7.6' where id = $UID_of_data_you_want_2_delete";
end the loop here (to allow for the remaining values in the array_of_UIDs[$index] to be deleted)
Think of it this way, suppose the GUI in which the data displayed was re-arranged, as happens automatically when you click the header label of each column in the display such that they are sorted ascending or descending, the checkbox indexes will change!! using the changed index will delete wrong data!
I hope you get the flow!! Dont be scared to ask again!!
PS: I code in Java but I get the flow of your code, that why my code looks wierd!