Ajax handler for tag search.

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

	$taxonomy        = sanitize_key( $_GET['tax'] );
	$taxonomy_object = get_taxonomy( $taxonomy );

	if ( ! $taxonomy_object ) {
		wp_die( 0 );
	}

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

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

	$comma = _x( ',', 'tag delimiter' );
	if ( ',' !== $comma ) {
		$search = str_replace( $comma, ',', $search );
	}

	if ( false !== strpos( $search, ',' ) ) {
		$search = explode( ',', $search );
		$search = $search[ count( $search ) - 1 ];
	}

	$search = trim( $search );

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

	/*
	 * Require $term_search_min_chars chars for matching (default: 2)
	 * ensure it's a non-negative, non-zero integer.
	 */
	if ( ( 0 == $term_search_min_chars ) || ( strlen( $search )  $taxonomy,
			'name__like' => $search,
			'fields'     => 'names',
			'hide_empty' => false,
			'number'     => isset( $_GET['number'] ) ? (int) $_GET['number'] : 0,
		)
	);

	/**
	 * Filters the Ajax term search results.
	 *
	 * @since 6.1.0
	 *
	 * @param string[]    $results         Array of term names.
	 * @param WP_Taxonomy $taxonomy_object The taxonomy object.
	 * @param string      $search          The search term.
	 */
	$results = apply_filters( 'ajax_term_search_results', $results, $taxonomy_object, $search );

	echo implode( "n", $results );
	wp_die();
}