Assigning individul post Id's to menu items

The key is here

echo '<li class="'. $class .'">' . $term->slug . '</li>';

This is what we call PHP concatenation. You can see more info on it here: https://php.net/manual/en/language.operators.string.php

Basically the code is just echoing a string. So, if you want to add a class to each li element, you need only do the following:

echo '<li class="someAmazingClassHere '. $class .'">' . $term->slug . '</li>';

Notice I left a space after the class, that’s because your current class will be appended inside there based on the PHP var.

If you want a different class in each iteration of the loop, you could concatenate a number to $class that is incremented in each iteration.

$i = 1;
foreach ($terms as $term) {
   $class = $current->slug == $term->slug ? 'current' : 'notCurrent' ;
   $class .= $i;
   echo '<li class="'. $class .'">' . $term->slug . '</li>';
   $i++;
}

Thanks guys that was so incredibly helpful. You’ve saved my ass!

For anyone else interested i made a slight addition to the code above from bcworkz, so that it each list-item would have the current or notCurrent class followed by ‘item1’, ‘item2’ etc.

<?php
	 // Get terms for post
	 $currentterm = get_the_terms( $post->ID , 'product-types' );
	 // Loop over each item since it's an array
	 if ( $currentterm != null ){
	 foreach( $currentterm as $current ) {
	} }

	$terms = get_terms('product-types', array(
	 	'orderby'    => 'ID',
	 )); 

	$i = 1;
	foreach ($terms as $term) {
	   $class = $current->slug == $term->slug ? 'current' : 'notCurrent' ;
	   $class .=  ' item';
	   $class .=  $i;
	   echo '<li class="'. $class .'">' . $term->slug . '</li>';
	   $i++;
	}
	unset($current);
?>

I do have a follow-up question if anyone can help.

This code brings up an error on pages where the ‘product-types’ term doesnt exist. I guess i need to put in something that checks for this term before it runs the code?

Yes you do. Something like what was done with $currentterm should work. Wrap everything I gave you previously with something like

if ( $terms != null ){
   // previous code here
}

Generally speaking, PHP is particular about trying to use variables that either are undefined or have no usable value. Any time there’s any chance of this you need to do protective checks like != null, isset(), array_key_exists(), etc., depending on the specific situation.

If there’s any chance the taxonomy does not exist, you should also check && ! is_wp_error( $terms )

That’s brilliant, thanks once again!