$year = 2021;
$is_leap_year = ((($year % 4) == 0) && ((($year % 100) != 0) || (($year % 400) == 0)));
echo $is_leap_year ? "yes" : "no" . "\n";
$year = 2024;
$is_leap_year = ((($year % 4) == 0) && ((($year % 100) != 0) || (($year % 400) == 0)));
echo $is_leap_year ? "yes" : "no" . "\n";
/*
run:
no
yes
*/