Here is a simple example of how I went about assigning a value to a custom field automatically.
Notes:
+ I used the https://www.advancedcustomfields.com/resources/acf-prepare_field/ prepare_field filter to accomplish this.
+ I set a Rule for the Field Group so that the field only gets displayed to the User *after* the Post is Published. This satisfies the criteria for: “default value couldn’t be changed by that user when creating new posts” (I also included an optional “read only” line of code to prevent any manual editing of the field – readonly can be set conditionally as well)
+ I also used the “field key” within the filter call. You can expose the “key” from the Screen Options tab at the top of the Edit Fields page.
+ Further criteria: Only update if the field doesn’t already have a value, and only update it for a specific User.
Here’s the code to store the IP Address of the User in a custom field on-the-fly (not overly useful, but serves as an example):
<?php
function my_acf_prepare_field( $field ) {
$field['readonly'] = true; // optionally make the field read-only
if ( $field['value'] ) { return $field; } // bail if field has a value already
$for_user = 2;
$current_user_id = (int)get_current_user_id();
if ( $current_user_id != $for_user ) { return $field; } // bail if not specified user
$ip = my_get_ip_function();
if ( $ip ) {
$field['value'] = $ip;
}
return $field;
}
add_filter('acf/prepare_field/key=field_59d7dc6ac103a', 'my_acf_prepare_field');
// this functions gets the IP Address
function my_get_ip_function() {
if ( !empty( $_SERVER['HTTP_CLIENT_IP'] ) ) {
$ip_address = $_SERVER['HTTP_CLIENT_IP'];
} else if ( !empty( $_SERVER['HTTP_X_FORWARDED_FOR'] ) ) {
$ip_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
} else {
$ip_address = $_SERVER['REMOTE_ADDR'];
}
return $ip_address;
}
?>
