$('.post-item').hover(
function() {
$(this).find('.post-gradient').css('background','linear-gradient(to top, rgba(0, 0, 0, 0.8) 0%, rgba(0, 0, 0, 0.2) 70%)');
},
function() {
$(this).find('.post-gradient').css('background','linear-gradient(to top, rgba(0, 0, 0, 0.5) 0%, rgba(0, 0, 0, 0.2) 70%)');
}
);