Make user autojoin to the current Group if They register from group page using Bp Ajax registration plugin

class BPAjaxR_Autojoin_Current_Group{

    private static $instance;

    private function __construct() {

        add_action( 'bp_after_account_details_fields', array( $this, 'add_group_field' ) );        
        add_action( 'bp_signup_usermeta', array( $this, 'update_signup_meta' ) );        
        add_action( 'bp_core_activated_user', array( $this, 'join_on_activation' ), 10, 3 );        

    }

    /**
     * Get the singleton instance
     * @return BPAjaxR_Autojoin_Current_Group
     */
    public static function get_instance(){

        if( !isset ( self::$instance ) )
                self::$instance = new self();

        return self::$instance;

    }
    /**
     * add current group as hidden field on registration page
     */
    public function add_group_field() {

        if( !bp_is_group() )
            return ;

        echo "<input type='hidden' name='current-group' value='". bp_get_group_id( groups_get_current_group() )."' />";        
    }

    /**
     * Add the group field to signup meta
     * @param type $meta 
     */
    public function update_signup_meta( $meta ) {

        //check if the group field is set
        if( $_POST['current-group'] )
            $meta['group_to_join'] = (int) $_POST['current-group'];

        return $meta;        
    }

    /**
     * Make user join the group when account is activated
     * @param type $user_id
     * @param type $key
     * @param type $user 
     */
    public function join_on_activation( $user_id, $key, $user ) {

        $meta = $user['meta'];

        if( empty( $meta['group_to_join']))
            return ;

        $group_id = (int) $meta['group_to_join'];

        groups_join_group($group_id, $user_id );        

    }


}
//initialize
BPAjaxR_Autojoin_Current_Group::get_instance();

Please put the above code in bp-custom.php

#bp-hacks, #registration #bp-ajax-registration