set_error_handler with PRIVATE-static-method callback

Question

Is it possible to use private static method as a set_error_hander callback?

This works fine:

<?php
    class DisplayErrors{

        private static $email_address = '[e-mail]';

        public static function error_handler($number, $message, $file, $line, $vars) {
            // send error to email;
        }

        private static function toEmail(){
            // set_error_handler('self::error_handler');
            set_error_handler(__CLASS__ .'::error_handler');
        }

    }

This has no effect nor error:

<?php
    class DisplayErrors{

        private static $email_address = '[e-mail]';

        private static function error_handler($number, $message, $file, $line, $vars) {
            // changed to private static method;
        }

        private static function toEmail(){
            // set_error_handler('self::error_handler');
            set_error_handler('self::error_handler');
        }

    }

I have also tried:

set_error_handler(array('self','error_handler'));
// no effect no error
set_error_handler('&self::error_handler');
// invalid callback

Answer 1

If you're using PHP 7.1 or higher, the new closure::fromCallable method will allow you to do this.

    private static function toEmail(){
        set_error_handler(Closure::fromCallable('static::error_handler'));
    }

Closure::fromCallable() evaluates the callable argument in the scope where it's called, so it can accept private and protected methods when used within the class.