Force login into WordPress site

Solution:

Try the following code. Write in your functions.php

 function custom_login() {
    $creds = array();
    $creds['user_login'] = 'myusername';
    $creds['user_password'] = 'mypassword';
    $creds['remember'] = true;
    $user = wp_signon( $creds, false );
    if ( !is_wp_error( $user ) ) {      
        wp_clear_auth_cookie();
        wp_set_current_user ( $user->ID );
        wp_set_auth_cookie  ( $user->ID );

        if($user->ID == 0) {
            echo 'faild login';
        } else {
            echo 'success';

        }


    } else {

                    echo "The username and password you entered don't match."; 

    }
        die();
    }
add_action('wp_login', 'custom_login');