Capabilities don't add

Question

I've wrote this code.

function wpo_install() {
    update_option( 'wpo_version', WPO_VERSION );

    wpo_add_caps();
    wpo_add_roles();

    set_transient( '_wpo_activation_redirect', true );
}
register_activation_hook( WPO_ROOT, 'wpo_install' );

In another file:

global $wpo_shared_caps;
$wpo_shared_caps = array(
    'edit_wp_orders',
    'edit_wp_order',
    'edit_others_wp_orders',
    'read_wp_order',
    'read_private_wp_orders',
    'delete_wp_order'
);

function wpo_add_caps() {
    global $wpo_shared_caps;

    $admin_caps = array(
        'backup_settings',
        'view_full_reports',
        'get_report_output'
    );
    $admin_caps = array_merge( $admin_caps, $wpo_shared_caps );
    $admin = get_role( 'administrator' );

    foreach( $admin_caps as $admin_cap ) 
        $admin->add_cap( 'administrator', $admin_cap );

}

function wpo_add_roles() {
    remove_role( 'accountant' );
    remove_role( 'employer' );

    global $wpo_shared_caps;

    $read_caps = array(
        'read_wp_order'              => true,
        'read_private_wp_orders'     => true
    );

    $acc_caps = array();
    foreach( $wpo_shared_caps as $cap )
        $acc_caps[ $cap ] = true;

    add_role( 'accountant', __( 'Accountant', 'wpo' ), $acc_caps );
    add_role( 'employer', __( 'Employer', 'wpo' ), $read_caps );
}

But these aren't working. Please help me. I've confused!

Answer 1

This line in your wpo_add_caps() function is incorrect:

$admin->add_cap( 'administrator', $admin_cap );

It should simply read:

$admin->add_cap( $admin_cap );

Source: WP_Role::add_cap().