Allow Select2 taggable input on custom taxonomy metabox for Wordpress

taggable-taxonamy-input.php

<?php
// I wanted to be able to use Select2's tagging feature to add new terms to posts in wordpress. I slighlty modified the code from Misha Rudrastyh's excelent tutorial(link below). Comments are closed on that post so I figured I'd post this gist for anyone else wanting to do this. Here's the portion of code I modified:
// @https://rudrastyh.com/wordpress/select2-for-metaboxes-with-ajax.html

// Note: if you'd like to limit selection you can remove "multiple="multiple"" from the select box, 
//or you can use Select2's "maximumSelectionLength" feature to limit to any number.

function rudr_display_select2_metabox( $post_object ) {
	
	// do not forget about WP Nonces for security purposes
	
	// I decided to write all the metabox html into a variable and then echo it at the end
	$html = '';
	
	// always array because we have added [] to our <select> name attribute
    
    // Create an array of the current term_ids
    $term_ids = array();
    $term_objs = get_the_terms( $post_object->ID, 'your-taxonomy' );
    foreach ($term_objs as $term_obj){
        $term_ids[] = $term_obj->term_id; //Add the term_id to the array.
    }	
    
	/*
	 * It will be just a multiple select for tags without AJAX search
	 * If no tags found - do not display anything
	 * hide_empty=0 means to show tags not attached to any posts
	 */
	if( $tags = get_terms( 'your-taxonomy', 'hide_empty=0' ) ) {
		$html .= '<p><label for="rudr_select2_tags">Your Taxonomy:</label><br /><select id="rudr_select2_tags" name="rudr_select2_tags[]" multiple="multiple" style="width:99%;max-width:25em;">';
		foreach( $tags as $tag ) {
			$selected = ( is_array( $term_ids ) && in_array( $tag->term_id, $term_ids ) ) ? ' selected="selected"' : '';
			$html .= '<option value="' . $tag->name . '"' . $selected . '>' . $tag->name . '</option>'; //I used tag name instead of $tag->term_id for the value so that I could pass it to wordpress and it would handle creating a new term ID if it was a new term name.
		}
		$html .= '</select></p>';
	}
    
	echo $html;
}

function rudr_save_metaboxdata( $post_id, $post ) {
	$my-taxonomy = 'custom-taxonomy';
	$my-post-type = 'your-post-type';
		
		
	if ( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ) return $post_id;
 
	// if post type is different from our selected one, do nothing
	if ( $post->post_type == $my-post-type ) {
		if( isset( $_POST['rudr_select2_tags'] ) ){
            		$termIDs = $_POST['rudr_select2_tags'];
            		
			wp_set_object_terms($post_id, $termIDs, $my-taxonomy );
		}else{
			wp_delete_object_term_relationships($post_id, $my-taxonomy );
		}
	}
	return $post_id;
}