PHP

disableTimeRanges

$('#totimeofappointment').attr("placeholder", "To hh:mm").timepicker({
            timeFormat: 'h:mm p',
            interval: 15,
            minTime: '10:00',
            maxTime: '5:00pm',
            maxMinutes: 45,
            startTime: '10:00',
            dynamic: false,
            dropdown: true,
            scrollbar: true,
            disableTimeRanges: [ ['1:30pm', '2:30pm'], ['3pm', '4:01pm'] ]
            change: function (time) {
              }
});