grids-with-array-chunk.php

//row markup
$row = '<div class="row-fluid">%s</div>'

//$posts = whatever you are trying to put in a grid.
$span_divs = array();
foreach ( $posts as $post ) {
  //make a span box
  $span_divs[] = sprintf( "<div class="span4">%s</div>" , $post);
}
//chunk the array of grid items into a number if items
foreach ( array_chunk($span_divs, 3) as $spans ) {
  //pull the chunked array markup into the row markup and write it out
  echo sprintf($row, implode('', $spans));
}

nice