How to get a users list by who created them?

Question

I have two users with the capability to create other users. But their roles are not same.

1. Tom - Role is Administrator
2. Jackie - Role is CMS Manger (a custom created role)

Both have capability to create new users. CMS Manger gets this capability by following code:

add_action( 'after_setup_theme', 'add_caps_to_custom_roles' );
function add_caps_to_custom_roles() {
  $caps = array(
    'list_users',
    'edit_users',
    'create_users',
    'delete_users',
  );
  $roles = array(
    get_role( 'CMS Manager' ),
  );
  foreach ($roles as $role) {
    foreach ($caps as $cap) {
      $role->add_cap( $cap );
    }
  }
}

I have 120 users in the site now. But do not know who created whom. I want a list that shows :

• List of users created by tom- Tom's users
• List of users created by jackie- Jackie's users

I was referring this for a while : https://codex.wordpress.org/Function_Reference/get_user_by But seems that function has NO solution for the above type of list.

How can I create those lists?

Answer 1

I've found it.

/*** Adding extra field to get the the user who creates the another user during ADD NEW USER ***/
function custom_user_profile_fields($user){
    if(is_object($user))
        $created_by = esc_attr( get_the_author_meta( 'created_by', $user->ID ) );
    else
        $created_by = null;
    ?>
    <h3>Extra profile information</h3>
    <table class="form-table">
        <tr>
            <th><label for="created_by">Created By</label></th>
            <td>
                <input type="text" class="regular-text" name="created_by" value="<?php echo $created_by; ?>" id="created_by" /><br />
                <span class="description">The person who creates this user</span>
            </td>
        </tr>
    </table>
<?php
}
add_action( 'show_user_profile', 'custom_user_profile_fields' );
add_action( 'edit_user_profile', 'custom_user_profile_fields' );
add_action( "user_new_form", "custom_user_profile_fields" );

function save_custom_user_profile_fields($user_id){
    # again do this only if you can
    //if(!current_user_can('manage_options'))
      //  return false;

    # save my custom field
    update_user_meta($user_id, 'created_by', $_POST['created_by']);
}
add_action('user_register', 'save_custom_user_profile_fields');
add_action('profile_update', 'save_custom_user_profile_fields');

And then querying the users by the custom field created_by.. That's it..

Answer 2

I used the plugin Snippets to put this and other custom functions into the site. Keeps the functions.php file clean.