Categories from front-end, checkbox selection doesn't work

Question

I'm using the plugin Post from site, which sets up a WP front end writer. I changed some line of code because I need to select categories with checkboxes and not with a multiple select (as it was originally in the plugin). Unfortunately it doesn't work: there is a checkbox in the front end writer, now, but checking boxes just does nothing: the post is saved without categories.

Here's the code which handles the taxonomy selection:

public function get_taxonomy_list( $taxonomy ){
    $terms = get_terms($taxonomy, array(
        'hide_empty' => 0
    ));
    if (!$terms || empty($terms)) return '';
    //preg_match_all('/\s*<input class="(\S*)" value="(\S*)" type="checkbox">(.*)<\/input>\s*/', $terms, $matches, PREG_SET_ORDER);
    $out = apply_filters( 'pfs_taxonomy_label', "<label for='terms_$taxonomy'>Seleziona i corsi</label>", $taxonomy );
    foreach ($terms as $term){
        if (is_taxonomy_hierarchical($taxonomy))
            $out .= "<input class='{$term->term_taxonomy_id}' type='checkbox' value='{$term->term_taxonomy_id}' name='{$term->term_taxonomy_id}' /> {$term->name}<br />";
        else
            $out .= "<input class='{$term->term_taxonomy_id}' type='checkbox' value='{$term->name}' name='{$term->name}' /> {$term->name}";
    }
    $out .= "<br />\n";
    return apply_filters("pfs_{$taxonomy}_list",$out);
}

and here's the code which saves the post and the taxonomy (which I didn't change):

$postarr['tax_input'] = (array_key_exists('terms',$pfs_data)) ? $pfs_data['terms'] : array();
$post_id = wp_insert_post($postarr);

Answer 1

You changed the checkbox's name attribute value. You should use the same name value: terms[$taxonomy][]

This should fix the code:

if (is_taxonomy_hierarchical($taxonomy))
        //$out .= "<input class='{$term->term_taxonomy_id}' type='checkbox' value='{$term->term_taxonomy_id}' name='{$term->term_taxonomy_id}' /> {$term->name}<br />";
        $out .= "<input class='{$term->term_taxonomy_id}' type='checkbox' value='{$term->term_taxonomy_id}' name='terms[{$taxonomy}][]' /> {$term->name}<br />";
    else
        // $out .= "<input class='{$term->term_taxonomy_id}' type='checkbox' value='{$term->name}' name='{$term->name}' /> {$term->name}";
        $out .= "<input class='{$term->term_taxonomy_id}' type='checkbox' value='{$term->name}' name='terms[{$taxonomy}][]' /> {$term->name}";
}

Answer 2

I usually use http://codex.wordpress.org/Function_Reference/wp_set_post_terms

when setting taxonomies on post creation.

$post_id = wp_insert_post();
if($post_id){
   wp_set_post_terms($post_id, $postarr['tax_input'], 'category' );
}