ACF Bidirectional Relationships - advanced-custom-fields

Question

How can I get bidirectional relationships with different post types in advanced custom fields ?
I use this but it's not working https://www.advancedcustomfields.com/resources/bidirectional-relationships/
I want to get a parent post type 1 where the child (post type 2) is attached.

Answer 1

You should try this. Where field_5a67cc16e1169 and field_5b7d60a26c7b5 are your custom fields (just make inspect of the your ACF in WP admin to find your IDs).
add_filter('acf/update_value/key=field_5a67cc16e1169', 'acf_reciprocal_relationship', 10, 3); //edit this with your ID - field one
add_filter('acf/update_value/key=field_5b7d60a26c7b5', 'acf_reciprocal_relationship', 10, 3); //edit this with your ID - field two
function acf_reciprocal_relationship($value, $post_id, $field) {
// set the two fields that you want to create
// a two way relationship for
// these values can be the same field key
// if you are using a single relationship field
// on a single post type
// the field key of one side of the relationship
$key_a = 'field_5a67cc16e1169'; //edit this with your ID - field one
// the field key of the other side of the relationship
// as noted above, this can be the same as $key_a
$key_b = 'field_5b7d60a26c7b5'; //edit this with your ID - field two
// figure out wich side we're doing and set up variables
// if the keys are the same above then this won't matter
// $key_a represents the field for the current posts
// and $key_b represents the field on related posts
if ($key_a != $field['key']) {
// this is side b, swap the value
$temp = $key_a;
$key_a = $key_b;
$key_b = $temp;
}
// get both fields
// this gets them by using an acf function
// that can gets field objects based on field keys
// we may be getting the same field, but we don't care
$field_a = acf_get_field($key_a);
$field_b = acf_get_field($key_b);
// set the field names to check
// for each post
$name_a = $field_a['name'];
$name_b = $field_b['name'];
// get the old value from the current post
// compare it to the new value to see
// if anything needs to be updated
// use get_post_meta() to a avoid conflicts
$old_values = get_post_meta($post_id, $name_a, true);
// make sure that the value is an array
if (!is_array($old_values)) {
if (empty($old_values)) {
$old_values = array();
} else {
$old_values = array($old_values);
}
}
// set new values to $value
// we don't want to mess with $value
$new_values = $value;
// make sure that the value is an array
if (!is_array($new_values)) {
if (empty($new_values)) {
$new_values = array();
} else {
$new_values = array($new_values);
}
}
// get differences
// array_diff returns an array of values from the first
// array that are not in the second array
// this gives us lists that need to be added
// or removed depending on which order we give
// the arrays in
// this line is commented out, this line should be used when setting
// up this filter on a new site. getting values and updating values
// on every relationship will cause a performance issue you should
// only use the second line "$add = $new_values" when adding this
// filter to an existing site and then you should switch to the
// first line as soon as you get everything updated
// in either case if you have too many existing relationships
// checking end updated every one of them will more then likely
// cause your updates to time out.
//$add = array_diff($new_values, $old_values);
$add = $new_values;
$delete = array_diff($old_values, $new_values);
// reorder the arrays to prevent possible invalid index errors
$add = array_values($add);
$delete = array_values($delete);
if (!count($add) && !count($delete)) {
// there are no changes
// so there's nothing to do
return $value;
}
// do deletes first
// loop through all of the posts that need to have
// the recipricol relationship removed
for ($i=0; $i<count($delete); $i++) {
$related_values = get_post_meta($delete[$i], $name_b, true);
if (!is_array($related_values)) {
if (empty($related_values)) {
$related_values = array();
} else {
$related_values = array($related_values);
}
}
// we use array_diff again
// this will remove the value without needing to loop
// through the array and find it
$related_values = array_diff($related_values, array($post_id));
// insert the new value
update_post_meta($delete[$i], $name_b, $related_values);
// insert the acf key reference, just in case
update_post_meta($delete[$i], '_'.$name_b, $key_b);
}
// do additions, to add $post_id
for ($i=0; $i<count($add); $i++) {
$related_values = get_post_meta($add[$i], $name_b, true);
if (!is_array($related_values)) {
if (empty($related_values)) {
$related_values = array();
} else {
$related_values = array($related_values);
}
}
if (!in_array($post_id, $related_values)) {
// add new relationship if it does not exist
$related_values[] = $post_id;
}
// update value
update_post_meta($add[$i], $name_b, $related_values);
// insert the acf key reference, just in case
update_post_meta($add[$i], '_'.$name_b, $key_b);
}
return $value;
} // end function acf_reciprocal_relationship