Pre-fill ACF repeater sub-fields

functions.php

<?php

/**
 * Let's say we have an ACF repeater field with 2 sub-fields:
 * 
 *  Section
 *  - Title
 *  - Description
 * 
 * This code snippet will automatically load 3 instances of the Section, and pre-fill the titles.
 */

function my_acf_set_repeater( $value, $post_id, $field ){
	
	// Debug
	// var_dump($value);
    
	// If value is not FALSE, it means the repeater has already been edited 
	// before so we return the $value and exit
	if ($value !== FALSE) {
		return $value;
	}

	// field_61de7bd327949 is the key of the Title sub-field we want to set
	// Define the $value array with 3 sub-arrays to set the Titles
	$value = array(
		array(
			'field_61de7bd327949' => 'Section Title One',
		),
		array(
			'field_61de7bd327949' => 'The Next Section',
		),
		array(
			'field_61de7bd327949' => 'Another Section Title',
		)
	);
	return $value;
}

// acf/load_value/name={$field_name} - filter for a specific value load based on it's field name
add_filter('acf/load_value/name=section', 'my_acf_set_repeater', 1, 3);