diasuteis.php

<?php

$datainicio = date('Y-m-d');
$diasuteis = 120;
$restante = $diasuteis+1;

	for($i = 0; $restante>0; $i++):

		$thisdata = strtotime('+'.$i.' day', strtotime($datainicio));
		$thisdiasemana = date('N', $thisdata);

		if($thisdiasemana < 6):
			$restante--;
		endif;

	endfor;

	echo date('d/m/Y', $thisdata);

?>