Like so:
function my_validate_username( $valid, $username ) {
$sanitized = sanitize_user( $username, false );
$valid = ( $sanitized == $username );
return $valid;
}
add_filter('validate_username', 'my_validate_username', 10, 2);
Like so:
function my_validate_username( $valid, $username ) {
$sanitized = sanitize_user( $username, false );
$valid = ( $sanitized == $username );
return $valid;
}
add_filter('validate_username', 'my_validate_username', 10, 2);