get date from float number in php or jquery

I am working on a project in which i have to Generate a Date from Selected Option value.

Example:

1. If selected 1.5 then need a date after 1 Month 15 days 15-08-2017

2. If selected 1.0 then need a date after 1 Month 17-08-2017

   <select class="form-control" name="days" id="days" required>
       <option data-days="1.5" value="3">After 1 month 15 days</option>
       <option data-days="2.5" value="4">After 2 month 15 days</option>
       <option data-days="6.0" value="10">After 5 month</option>
       <option data-days="7.5" value="30">After 7 month 15 days</option>       
       //And So on...
   </select>
   
   // Here is the script for getting selected option days attribute.
   $('body').on('change', '#days', function(e) {
       var days = $(this).find(':selected').data('days');
   
       // Now How do i get the date according the days. as shown in example
   
   });
   

I have also tried to get the date in PHP but i didn't get it.

$date = date('Y-m-d', strtotime('+1.0 month'));

So can anyone help me to get date using this float numbers in PHP or Jquery.