---
title: 'Advanced Custom Fields - update_sub_field() for repeater fields'
url: 'https://www.nick-hayward.co.uk/advanced-custom-fields-update_sub_field-for-repeater-fields'
markdown: 'https://www.nick-hayward.co.uk/advanced-custom-fields-update_sub_field-for-repeater-fields.md'
date: '2022-10-20'
description: "I've been working on a WordPress web design project using a hand made front-end form to update an Advanced Custom Fields repeater field via AJAX. This was a bit of a stretch for me as I've never used AJAX before and I hit a wall when 99% there!"
taxonomy:
category:
- 'Web Development'
- WordPress
---
[Home](https://www.nick-hayward.co.uk/) » Advanced Custom Fields - update\_sub\_field() for repeater fields
October 20th, 2022 Posted in [Web Development](https://www.nick-hayward.co.uk/taxonomy?name=category&value=Web%20Development), [WordPress](https://www.nick-hayward.co.uk/taxonomy?name=category&value=WordPress)
# Advanced Custom Fields - update\_sub\_field() for repeater fields
I’ve been working on a WordPress web design project using a hand made front-end form to update an [Advanced Custom Fields](https://www.advancedcustomfields.com/) repeater field via AJAX. This was a bit of a stretch for me as I’ve never used AJAX before and I hit a wall when 99% there!
I hit a snag with the **update\_sub\_field()** function to target the right repeater row and field to update. There were two issues – one is that the rows don’t start from 0 like I expected and there’s a functions.php snippet to fix that ([bottom of this page](https://www.advancedcustomfields.com/resources/update_sub_field/)).
The second was that the [documentation](https://www.advancedcustomfields.com/resources/update_sub_field/) was a bit ambiguous in describing how the data needs to be sent to the back end (for someone unfamiliar with arrays, like me), with this example being given:
```
// target a nested sub field directly.
update_sub_field( array('repeater', 1, 'sub_repeater', 2, 'sub_sub_field'), 'This value is for repeater row 1, and sub_repeater row 2!' );
```
I replicated this with my incoming data from the AJAX function but it wouldn’t update unless I hard coded it in the **update\_sub\_field()** PHP function. I thought the data was exactly the same, but it actually wasn’t – it had quote marks around it so was being treated like a string rather than converted to an array.
ACF support suggested making sure the array was sent back correctly and a developer friend fixed this quickly by exploding the query string into an array before passing it to **update\_sub\_field()**
Part of my PHP function that the AJAX call sends data back to:
```
$post_id = $_POST['post-id'];
$memberName = $_POST['member-name'];
$acfPath = $_POST['acf-path'];
// Convert the query string to array - thanks Ewan!
$combined = explode(",", $acfPath);
// Now sending $combined instead of the raw query string in $acfPath
update_sub_field($combined, $memberName, $post_id);
```
So that fixed things and I hope this quick blog helps anyone else struggling with **update\_sub\_field()** updating the Repeater field in Advanced Custom Fields
---
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