Block embedding from other websites

function is_allowed_referer() {

    $self = parse_url( home_url('/') );

    $search_engine_terms = [ 'google', 'bing', 'yahoo', 'ask', 'duckduckgo', 'ecosia', $self['host'] ];

    $referer_url    = $_SERVER['HTTP_REFERER'];
    $referer_host   = parse_url( $referer_url, PHP_URL_HOST );

    foreach ( $search_engine_terms as $term ) {
        if( strpos( $term , $referer_host ) !== false ){
            return true;
        }
    }

    return false;
}

/**
 *
 * Block embedding from other websites
 *
 */
add_filter( 'streamtube/player/file/output', function( $player, $setup, $source ){
    if( is_embed() ){

        if( ! is_allowed_referer() ){
            $player = '';
        }
    }

    return $player;
}, 999, 3 );