Complicated while loop [on hold]

Please help me to solve this .The following html code need to looped using while loop in php .

<li>
<div class=”first”>

<div clas=”bg”>

<div clas=”sm”>

<div class="row">
1
</div>
<div class=”rowss”>
<div class=”1”>
2
</div>
<div class=”1”>
3
</div>
</div>
</div>
<div clas=”sm”>
<div class=”rowss”>
<div class=”1”>
4
</div>
<div class=”1”>
5 
</div>
</div>
 <div class="row">
6
 </div>
 </div>
 </div>
 </div>
 </li>

This is the first li .The second li is the some copy of the first li ,but the numbers are 7 , 8 ,9, 10, 11, 12. for next li it should be 13,14,15,16,17,18. it repeats.

total number of elements in loop is 24(eg).