get_terms orderby numeric

Question

I am trying to order my terms numeric. But the problem is that nog every term is numeric. So I have the following terms (check image below) which some of them are dimensions and some are others. As you can see, my get_terms() function, orders them by name, but if they are numeric it only looks at the first character. So 1400mm is less than 500mm.

I don't know where I need to begin. Should I try to modify the result of get_terms() or hook into the get_terms_orderby() function. But I have no idea how to do this.

My code to show the terms:

<?php
$taxonomy = 'product-filter';
$parents = get_terms( $taxonomy, array( 'hide_empty' => false, 'parent' => 0, 'orderby' => 'id' ) );
if( ! empty( $parents ) ) {
    foreach( $parents as $parent ) {
        echo '<ul>';
        echo '<h2>' . $parent->name . '</h2>';
        $children = get_terms( $taxonomy, array( 'hide_empty' => false, 'child_of' => $parent->term_id ) );
        foreach( $children as $child ) {
            echo '<li><label><input type="checkbox">' . $child->name . ' (' . $child->count . ')</label></li>'; 
        }
        echo '</ul>';
    }
}
?>

Answer 1

You can use usort to sort the object $children.

The function to sort after you got the $children object can be like this:

usort( $children, function($a, $b) {
    $ai = filter_var($a->name, FILTER_SANITIZE_NUMBER_INT);
    $bi = filter_var($b->name, FILTER_SANITIZE_NUMBER_INT);
    if ($ai == $bi) {
        return 0;
    }
    return ($ai < $bi) ? -1 : 1;
});