I had a problem with Revolution Slider on a WordPress installation when upgrading to PHP 7.2+. It would generate the error – PHP Fatal error:  operator not supported for strings in C:[path]\wp-content\plugins\revslider\includes\framework\base-admin.class.php:71
The problem was from the plugin attempting to use the short array push syntax on a string:
$box = array(); $box['title'] = $title; $box['location'] = $location; $box['content'] = $content; $box['draw_function'] = $customDrawFunction; self::$arrMetaBoxes = $box;
The solution was to modify the last line as such:
self::$arrMetaBoxes = $box;
No explosions, so all is well!
This discussion tipped me in the right direction: https://stackoverflow.com/questions/5879675/problem-with-fatal-error-operator-not-supported-for-strings-in