Código PHP:
function difdias ($diainicial,$diafinal) {
$day = substr($diainicial,8,2);
$month = substr($diainicial,5,2);
$year = substr($diainicial,0,4);
if (!checkdate($month,$day,$year)) {return false; }
$dia[0] = date("l",mktime(0,0,0,$month,$day,$year));
$day = substr($diafinal,8,2);
$month = substr($diafinal,5,2);
$year = substr($diafinal,0,4);
if (!checkdate($month,$day,$year)) {return false; }
$dia[1] = date("l",mktime(0,0,0,$month,$day,$year));
for ($a=0;$a<=1;$a++) {
switch ($dia[$a]) {
case "Monday":
$dia[$a] = 1;
break;
case "Tuesday":
$dia[$a] = 2;
break;
case "Wednesday":
$dia[$a] = 3;
break;
case "Thursday":
$dia[$a] = 4;
break;
case "Friday":
$dia[$a] = 5;
break;
case "Saturday":
$dia[$a] = 6;
break;
case "Sunday":
$dia[$a] = 7;
break;
}
}
if ($dia[0] > $dia[1]) { $dia[0] -= 7; }
return $dia[1] - $dia[0];
}
echo difdias("2005-01-01","2005-01-12");