ProjectID - JobID Row Remains Visible

I have a page that contains PHP and Javascript. I have a table of results, with two grouping stages:

- Month, Year1
- ProjectID1
- Job ID1
- Job ID2
- ProjectID2
- Job ID1
- Month, Year2
- ProjectID3
- Job ID1
- ProjectID4
- Job ID1

The problem is that when the ProjectID row is opened to display the JobID row, then close the Month, Year row, the JobID row remains visible.

Here is the code:
//JAVASCRIPT
Code:
function toggle2(id, obj) {
var matchingElements = new Array();
if (document.getElementsByClassName) {
matchingElements = document.getElementsByClassName(id);
} else { .....