foo.php

<?php
	function foo(){
		// Stuff
		
		$output = array(
			'size'=>12-$size,
			'colour'=>$colour,
			'hostname' => $hostname
		)
		
		return $output;
	}

	$output = foo();
?>

<div class="col-<?= $output['size']; ?>"></div>
<div class="col-<?= $output['size']; ?> bg-<?= $output['colour']; ?> text-white alert-<?= $output['colour']; ?>>
<h4 class="alert-heading"><?= $output['hostname']; ?></h4>