Hi Josh!

implode-me-classes.php

<?php

$classes = [];


// bunch of code

if( some condition) {
	$classes[] = 'has-thumbs';
}

// bunch of code

if( .. IDK ... count( $array_bla ) > 4) {
	$classes[] = 'webmasters-went-cray-cray';
}


// to be super super super super safe
array_walk($classes, function( $class_name ) {
	return sanitize_title($class_name);
});

?>
<div class="container <?php echo implode(' ', $classes); ?>"></div>