Base-admin.class.php PHP Fatal error: Uncaught Error: [] operator not supported for strings

The error you're encountering, "PHP Fatal error: Uncaught Error: [] operator not supported for strings", indicates that in the file base-admin.class.php of the Revolution Slider (or RevSlider) plugin, you are trying to use the [] operator to add a value to a variable that has been declared as a string. The [] operator is used [...]