Noticed another mistake: This test needs to go from 0 to sizeof -1, as auto-indexed arrays start with item 0.
PHP Code:
for($i=1; $i<=sizeof($middleboxes_group); $i++) { 
PHP Code:
for($i=0; $i<=sizeof($middleboxes_group)-1; $i++) { 
or
PHP Code:
for($i=0; $i<sizeof($middleboxes_group); $i++) {