wordpress: Convert string duration to ISO 8601 duration format

gistfile1.txt

/* Convert string duration to ISO 8601 duration format.
=========================================================================== */
function itl_iso8601_duration( $seconds ) {
    $hours   = floor( $seconds / 3600 );
    $seconds = $seconds % 3600;

    $minutes = floor( $seconds / 60 );
    $seconds = $seconds % 60;

    $iso8601 = sprintf( 'PT%s%s%s',
                    $hours > 0 ? ( $hours < 10 ? '0' . $hours : $hours ) . 'H' : '',
                    $minutes > 0 ? ( $minutes < 10 ? '0' . $minutes : $minutes ) . 'M' : '',
                    ( $seconds < 10 ? '0' . $seconds : $seconds ) . 'S'
                );

    return $iso8601;
}