How to add Default Level-0 parent and Level-1 class in WordPress Category in li element?

Question

I just want to add a class if li is parent class should be level-0 and if li is the child then level-1 etc. I am using the following loop.

 <?php
    $categories = get_categories();
    foreach($categories as $category) {
       echo '<li class="here-i-want-to-add"><a href="' . get_category_link($category->term_id) . '">' . $category->name . '</a></li>';
    }
    ?>

Answer 1

The category object stores the parent ID like this: $category->parent

In the event that there is no parent it's equal to 0.

In this way, it is possible to create a variable equal to the parent class or the child parent according to the value of $category->parent:

$categories = get_categories();
if ( ! is_wp_error( $categories ) ) {
    foreach ( $categories as $category ) {
        $htmlclass = ( $category->parent === 0 ) ? "level-0" : "level-1";
        echo '<li class="' . esc_attr( $htmlclass ).'">';
        echo '<a href="' . esc_url( get_category_link( $category->term_id ) ) . '">';
        echo esc_html( $category->name );
        echo '</a></li>';
    }
}

Answer 2

Greatly inspired by @Sabry's answer.

Term nesting depth is taken into consideration. Also it is one-size-fits-all to work with any taxonomy.

<?php
$taxonomy = 'category'; // your requred

$terms = get_terms(
    array(
        'taxonomy' => $taxonomy,
    )
);

if ( ! is_wp_error( $terms ) ) {
    foreach ( $terms as $term ) {
        $term_ancestors = get_ancestors( $term->term_id, $taxonomy, 'taxonomy' );

        $term_nesting_depth = count( $term_ancestors );

        $htmlclass = 'level-' . $term_nesting_depth;

        echo '<li class="' . esc_attr( $htmlclass ) . '">';
        echo '<a href="' . esc_url( get_term_link( $term, $taxonomy ) ) . '">';
        echo esc_html( $term->name );
        echo '</a></li>';
    }
}