import-terms.php

<?php
/*
Plugin Name: Import terms
Plugin URI: https://www.philwylie.co.uk/
Description: Given an array of terms, import into a specified taxonomy. Tool to help format array - https://link.from.pw/2tM8iEs
Version: 1.0.0
Author: Phil Wylie
Author URI: https://www.philwylie.co.uk/
License: GPL2
*/

function iweb_import_terms() {
	if ( ! isset( $_GET['import-terms'] ) ) {
		return;
	}

	$taxonomy = 'taxonomy';

	$terms = array(
		'Term 1',
		'Term 2',
	);

	foreach ( $terms as $term ) {
		wp_insert_term( $term, $taxonomy );
	}

	exit;
}
add_action( 'init', 'iweb_import_terms' );