Thank you for your quick reply. Unfortunately, problem is not solved. as I told it’s wrong with this code
function hatchbuckCode() {
echo get_post_custom_values(‘metabox’)[0];
}
if I comment out this echo get_post_custom_values(‘metabox’)[0]; line then plugin can be activated. So I think, it’s something related to php version.
My site is running on PHP version: 5.3.28