Custom taxonomy, get_the_terms, listing in order of parent > child

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I have a hierarchical custom taxonomy which I can display using print_r(get_the_terms( $post->ID, 'taxonomic_rank' ));:

Array
(
    [46] => stdClass Object
        (
            [term_id] => 46
            [name] => Aplocheilidae
            [slug] => aplocheilidae
            [term_group] => 0
            [term_taxonomy_id] => 53
            [taxonomy] => taxonomic_ranks
            Custom taxonomy, get_the_terms, listing in order of parent > child => 
            [parent] => 39
            [count] => 1
            [object_id] => 443
        )

    [47] => stdClass Object
        (
            [term_id] => 47
            [name] => Aplocheilus
            [slug] => aplocheilus
            [term_group] => 0
            [term_taxonomy_id] => 54
            [taxonomy] => taxonomic_ranks
            Custom taxonomy, get_the_terms, listing in order of parent > child => 
            [parent] => 46
            [count] => 1
            [object_id] => 443
        )

    [39] => stdClass Object
        (
            [term_id] => 39
            [name] => Cyprinodontiformes
            [slug] => cyprinodontiformes
            [term_group] => 0
            [term_taxonomy_id] => 52
            [taxonomy] => taxonomic_ranks
            Custom taxonomy, get_the_terms, listing in order of parent > child => 
            [parent] => 0
            [count] => 1
            [object_id] => 443
        )

)

This taxonomy will always take the following form:
Order (parent) > Family (child of Order) > Sub-family (child of Family)

Is there a quick and easy way of displaying these taxonomies in the correct order, so that I could print out the following line? Order: <order>, Family: <family>, Sub-family: <sub-family>

Thanks in advance

7 s
7

There are probably some better ways to do this but you can always do a three simple foreach loops.

I wrote an example function that does the job well and should serve you as a good starting point:

function print_taxonomic_ranks( $terms="" ){

    // check input
    if ( empty( $terms ) || is_wp_error( $terms ) || ! is_array( $terms ) )
        return;

    // set id variables to 0 for easy check 
    $order_id = $family_id = $subfamily_id = 0;

    // get order
    foreach ( $terms as $term ) {
        if ( $order_id || $term->parent )
            continue;
        $order_id  = $term->term_id;
        $order     = $term->name;
    }

    // get family
    foreach ( $terms as $term ) { 
        if ( $family_id || $order_id != $term->parent )
            continue;
        $family_id = $term->term_id;
        $family    = $term->name;
    }

    // get subfamily
    foreach ( $terms as $term ) { 
        if ( $subfamily_id || $family_id != $term->parent ) 
            continue;
        $subfamily_id = $term->term_id;
        $subfamily    = $term->name;
    }

    // output
    echo "Order: $order, Family: $family, Sub-family: $subfamily";

}

Let it live in your functions.php file and use it in your templates like this:

print_taxonomy_ranks( get_the_terms( $post->ID, 'taxonomic_rank' ) );

NOTE: Looping the same array three times around sounds a bit stupid but on the other hand it’s a quick and easy solution which is easy to read, extend and maintain.

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