Ensuring that the filter priority was more than 10 didn’t fix the problem. Here is the full code for the filter:
/**
* Modify fields on load based on our advanced settings
*/
function tgmembership_modify_acf_field_on_load( $field ) {
// get plugin settings
$options = get_option( 'tgmembership_options' );
// get names of fields that should be read-only
$readonly_fields = array_map('trim', explode(",", $options["acf_readonly"]));
// loop each readonly slug and set the disabled flag on those fields
foreach ($readonly_fields as $name) {
if ($field["name"] == $name) {
$field['disabled'] = 1;
}
}
// return the field
return $field;
}
add_filter('acf/load_field', 'tgmembership_modify_acf_field_on_load', 16);
I really think that ACF just isn’t respecting the disabled flag when adding fields to the User Profile. If that is the case then maybe I just can’t use ACF for the fields I want read-only (there are a few others I need to do manually anyway as they’re more complex, so that wouldn’t be a real problem). But I’d consider that a bug in ACF.
