This can be used in anything, but I recently had the pleasure of working with Owl Carousel and a client needed to group 3 images in a owl carousel slide, this PROPERLY groups elements into a div without creating an orphan div group towards the end.

owl-carousel-group-items-into-divs.php

<?php
/*
Cleaner Code
*/
  // a psudeo array of images for testing
	$items = array(
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',		
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
	);
  
  // set the inital increment
	$z = 1;
	
	// every X images make them into a group
	$divider = 3; 
	
	// define a new line so code looks neat
	define("NL","\r\n");

	// if items exist 
	if( count($items) ) :
		// html comment
		echo "<!-- bof: owl-single -->" . NL;	
		// new line
		echo NL;
		// add the owl slider wrapper
		echo "<div class='owl-single'>" . NL  . NL;						
			// add a group to the slider which will hold as many images that the divider specifies above
			echo "\t" . "<div class='owl-group'>" . NL;			
				foreach($items as $index=>$image) :		
					// insert image into group
					echo "\t\t" . "<img src='$image' alt=''>"  . NL;					
					// if current image is the last image or the current image is the last image in the items array, close off the group
					if($z % $divider == 0 || $z == count($items) ){
						echo "\t" . "</div>" . NL . NL;												
						// only open a new div if there are more images to be added, do not add an orphan div, this would create an empty slide in owl carousel
						if( $z < count($items) ) :
							echo "\t" . "<div class='owl-group'>"  . NL;						
						endif;
					}
					// incremement					
					$z++;
				endforeach;													
		// close off the .owl-single div
		echo "</div>" . NL;
		// new line
		echo NL;
		// HTML comment
		echo "<!-- eof: owl-single -->" . NL;	
	endif;
?>

<?php
/*
No comments or newline/tabs added
*/

$items = array(
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',		
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
		'https://s-media-cache-ak0.pinimg.com/236x/77/85/a1/7785a1b13a780842309579574715c35c.jpg',
	);

	$z = 1;
	$divider = 3; 
		
	if( count($items) ) :
		echo "<div class='owl-single'>" ;									
			echo "<div class='owl-group'>";			
				foreach($items as $index => $image) :							
					echo "\t\t" . "<img src='$image' alt=''>" ;										
					if($z % $divider == 0 || $z == count($items) ){
						echo "</div>";																		
						if( $z < count($items) ) :
							echo "<div class='owl-group'>" ;						
						endif;
					}				
					$z++;
				endforeach;													
		echo "</div>";				
	endif;

?>