how cant i sort an array in to div in pairs (odd and even) ?

hello

how cant i sort an array in to div in pairs (odd and even) ?

so i have the numbers 1 to 50 for a book

i want the first number and last number to be front and back pages.

ie.

1

2+3

3+4

4+5

5+6

7

this is the div structure

im giving the front cover a class of fCover then left for the left pages and right for the right pages.

<div class="bb-custom-wrapper">
<div id="bb-bookblock" class="bb-bookblock">
                
        //FRONT PAGE      
	<div class="bb-item" id="item1">
	    <div class="content">
		<div class="scroller fCover">
		<img src="assets/images/pages/1.jpg" ALT="page1">
		</div>
	    </div>
	</div>
                    
                    
	//PAGES 2 & 3
        <div class="bb-item" id="item2">
            <div class="content">

                //PAGE 2
		<div class="scroller left">
		     <img src="assets/images/pages/2.jpg" ALT="page2">
		</div>

                //PAGE 3
                <div class="scroller right">
		     <img src="assets/images/pages/3.jpg" ALT="page3">
		</div>
	    
            </div>
	</div>

</div>
</div>

This is the php that i have:

<div class="bb-custom-wrapper">
<div id="bb-bookblock" class="bb-bookblock">
                
   <?php
	foreach($pageImg as $file){
	echo'
	<div class="bb-item" id="item'.$file.'">
		<div class="content">';
						
		if($file == "1"){
		echo'
		<div class="scroller fCover">
		<img src="assets/images/pages/'.$file.'.jpg" ALT="page'.$file.'">
		</div>';
		}
		echo'	
		</div>
	</div>';
	}?>
                    
</div></div>

that give me the first page but im stuck on the paired pages ?

thanks

rick