Populate Field Value with Sum of Two Other Fields

• dlovas

• January 6, 2018 at 6:13 am

I would like to populate the value of a field with the sum of two other numeric fields in the same post. For example:

field1 + field2 = field3 –> on insert or update of post.

So any time I add or update a post, it does the calculation and adds/update field3 with the result.

All fields are numeric acf.

Is there a function that exists for this, or one that I can modify to make this work?

I prefer to do the calculation “on post insert/update” rather than on the front-end since I have other calculations to perform on the front-end.

• John Huebner

• January 7, 2018 at 12:17 am

There is a filter that runs when acf inserts or updates fields https://www.advancedcustomfields.com/resources/acf-save_post/

You would create a filter function and in this function get the values from the 2 fields and then update the 3rd field https://www.advancedcustomfields.com/resources/update_field/

• dlovas

• January 7, 2018 at 5:27 am

John,

Thanks for pointing me to the two functions as a starting point. I was able to put together the following, and it worked perfect. Appreciate the help.

Code:

function my_acf_save_post( $post_id ) {
    
// get new value
$costInDollars = get_field('cost_in_dollars');
$discountInDollars = get_field('discount_in_dollars');
    
// do something
$totalCostInDollars = $costInDollars - $discountInDollars;
update_field('total_cost_in_dollars', $totalCostInDollars, $post_id);
	
}

add_action('acf/save_post', 'my_acf_save_post', 20);

• LPogg

• November 8, 2019 at 2:46 am

Hi, is this for frontend?
I need to do the same in the Backend, like this thread
https://support.advancedcustomfields.com/forums/topic/how-to-create-a-field-as-sum-of-two-other-fields/

What type of field should I use for the 3rd field?
Thanks!

• jrstaton

• August 11, 2020 at 9:08 am

Would I need to do anything differently to get this to work with a repeater field inside flexible content?

I was able to get it to work fine outside of the repeater. Once I put it inside the repeater I used get_sub_field instead of get_field but that didn’t seem to do anything. Any ideas?

Thanks in advance!

• John Huebner

• August 11, 2020 at 9:15 pm

You would need to loop over the flex field and loop over the repeater, just like you if you were going to display the flex/repeater on the front end of the site. Then use get_sub_field() and update_sub_field() https://www.advancedcustomfields.com/resources/update_sub_field/

• jrstaton

• August 12, 2020 at 12:52 am

Thanks. I actually have Repeater > Flexible Content > Repeater. After working with the information from the support article you posted I got it working. Here is what worked.

function my_acf_save_post( $post_id ) {
if( have_rows('content_panels') ): 
	$parent_i = 0;
	while( have_rows('content_panels') ): the_row();
	 $parent_i++;
 		if( have_rows('panel_contents') ):
			while( have_rows('panel_contents') ): the_row();
				if( have_rows('content_columns') ):
				$child_i = 0;
					while ( have_rows('content_columns') ) : the_row();	
					$child_i++;
					// get new value
					$topMargin = get_sub_field('column_margin_top');
					$bottomMargin = get_sub_field('column_margin_bottom');
						if($topMargin || $bottomMargin):
						$totalMargin = $topMargin + $bottomMargin;	
						update_sub_field('total_margin', $totalMargin, $post_id);
						endif;
					endwhile;
				endif;
			endwhile;
		endif;
	endwhile;
endif;
}
add_action('acf/save_post', 'my_acf_save_post', 20);

Is there a way to optimize what I have or is this correct? I just don’t want it to cause issues once I get into a production environment. Thanks again.