Save CTP post meta different values each day without overwriting previous values

Question

I have a Custom Post Type which fetches some data every day for each post and I need to store new values while keeping the old ones. If I use this, it will overwrite previous data:

update_post_meta(get_the_ID(), 'temperature', 25);
update_post_meta(get_the_ID(), 'humidity', 70);
update_post_meta(get_the_ID(), 'ph', 7);

So I was thinking about using something like this to append time to name:

    update_post_meta(get_the_ID(), 'temperature-' . time(), 'some_value');
    update_post_meta(get_the_ID(), 'humidity-' . time(), 'some_value');

I got all this working, and now I got to the point where I want to retrieve the latest two data for each post - values for yesterday and today. This is where I got stuck.

Is there an easier/Wordpress way for saving the different data every day for every variable inside every CTP post?

When retrieving these variables I was hoping to do it something like this, but maybe I have complicated more than I should have?

  $args = array(
        'post_type' => 'myctp',
        'posts_per_page' => -1 // Retrieve all CTP posts
        );
  $query = new WP_Query($args);

    if($query->have_posts())   :
         while($query->have_posts())  {

             $query->the_post();
             $post_meta = get_post_meta(get_the_ID());

             // here get only 2 latest values for temperature, humidity, ph...

         }
    endif;

Answer 1

I'm agree with the comment of @birgire, but if you really want to do it with custom fields, I think it's better to group all datas for a post in one custom field in an array.

After, you only need to use get_post_meta to get older values and add the new one in the array. Eventually, you could apply a php function to the array limite to 5 days. update_post_meta will save it as an array, to get it in your template, just create a display function.