wp_ajax_ajax_tag_search()

function wp_ajax_ajax_tag_search() {
	if ( ! isset( $_GET['tax'] ) ) {
		wp_die( 0 );
	}

	$taxonomy = sanitize_key( $_GET['tax'] );
	$tax = get_taxonomy( $taxonomy );
	if ( ! $tax ) {
		wp_die( 0 );
	}

	if ( ! current_user_can( $tax->cap->assign_terms ) ) {
		wp_die( -1 );
	}

	$s = wp_unslash( $_GET['q'] );

	$comma = _x( ',', 'tag delimiter' );
	if ( ',' !== $comma )
		$s = str_replace( $comma, ',', $s );
	if ( false !== strpos( $s, ',' ) ) {
		$s = explode( ',', $s );
		$s = $s[count( $s ) - 1];
	}
	$s = trim( $s );

	/**
	 * Filters the minimum number of characters required to fire a tag search via Ajax.
	 *
	 * @since WP-4.0.0
	 *
	 * @param int         $characters The minimum number of characters required. Default 2.
	 * @param WP_Taxonomy $tax        The taxonomy object.
	 * @param string      $s          The search term.
	 */
	$term_search_min_chars = (int) apply_filters( 'term_search_min_chars', 2, $tax, $s );

	/*
	 * Require $term_search_min_chars chars for matching (default: 2)
	 * ensure it's a non-negative, non-zero integer.
	 */
	if ( ( $term_search_min_chars == 0 ) || ( strlen( $s ) < $term_search_min_chars ) ){
		wp_die();
	}

	$results = get_terms( $taxonomy, array( 'name__like' => $s, 'fields' => 'names', 'hide_empty' => false ) );

	echo join( "\n", $results );
	wp_die();
}