Full name search

user-search-by-name.php

/**
 * Search users by first/last name in addition to the built-in nicename search
 * @param string $wp_user_query User query
 * @return  string Modified user query
 */
function ws_user_search_by_name( $wp_user_query ) {
	if ( false === strpos( $wp_user_query->query_where, '@' ) && ! empty( $_GET['s'] ) ) {
		global $wpdb;

		$uids = array();

		// Remove markup and extra spaces from search string
		$qstr = sanitize_text_field( $_GET['s'] );

		// Get user ids from users that match first name, last name or full name
		$usermeta_affected_ids = $wpdb->get_results( "SELECT DISTINCT user_id, GROUP_CONCAT(meta_value SEPARATOR ' ') as full_name FROM $wpdb->usermeta WHERE (meta_key='first_name' OR meta_key='last_name') GROUP BY user_id HAVING full_name LIKE '%{$qstr}%'" );
		foreach ( $usermeta_affected_ids as $maf ) {
			array_push( $uids, $maf->user_id );
		}

		// Get user ids from users that match nicename
		$users_affected_ids = $wpdb->get_results( "SELECT DISTINCT ID FROM $wpdb->users WHERE LOWER(user_nicename) LIKE '%{$qstr}%'" );

		foreach ( $users_affected_ids as $maf ) {
			if ( ! in_array( $maf->ID, $uids ) ) {
				array_push( $uids,$maf->ID );
			}
		}

		// Modify the original user query,
		// replace search for nicename and instead use the array of user ids that we have collected
		$id_string = implode( ',', $uids );
		if ( ! empty( $id_string ) ) {
			$wp_user_query->query_where = str_replace( "user_nicename LIKE '%{$qstr}%'", "ID IN({$id_string})", $wp_user_query->query_where );
			$wp_user_query->query_where = str_replace( "user_nicename LIKE '{$qstr}'", "ID IN({$id_string})", $wp_user_query->query_where );
		}
	}
	return $wp_user_query;
}
add_action( 'pre_user_query', 'ws_user_search_by_name' );