A simple piece of code to do a simple operation - alternate background color of table rows.
If you are displaying a large amount of data within a table, a nice formating touch is to change the background of each alternate table row.
To do this, you simply need to check what row you are on. To do this we use the remainder operator %. For odd and even row coloring, check for a value in $rownumber%2. For every third row use $rownumber%3 and so on. Once you know which row you are on, set the background style accordingly. You could even define custom styles for each remainder value.