Deprecated ereg function breaks it

Having trouble with deprecated ereg() function. see
http://www.devthought.com/2009/06/09/fix-ereg-is-deprecated-errors-in-php-53/
Function ereg() is deprecated in /wp-content/plugins/get-post-image/phpthumb/phpThumb.config.php on line 34

Nowadays PhpThumb 1.7.13 has the line in phpthumb.config.default:

$PHPTHUMB_CONFIG['document_root'] = realpath((getenv('DOCUMENT_ROOT') && preg_match('#^'.preg_quote(realpath(getenv('DOCUMENT_ROOT'))).'#', realpath(__FILE__))) ? getenv('DOCUMENT_ROOT') : str_replace(dirname(@$_SERVER['PHP_SELF']), '', str_replace(DIRECTORY_SEPARATOR, '/', dirname(__FILE__))));

https://wordpress.org/plugins/get-post-image/