//task 1
 $day = 25;
if($day <=10){
    echo 'the number of first the decade';
}
elseif ($day <=20){
    echo 'the number of the second';
}
else { echo 'the number from the third decade';}


//task 2
$month = rand(1, 12);
if ($month <= 2 || $month == 12) {
    echo 'winter';
} elseif ($month > 2 && $month <= 5) {
    echo 'spring';
} elseif ($month > 5 && $month <= 8) {
    echo 'summer';
} else {
    echo 'autumn';
}


 // task 3
$year = 1004;
if ($year % 4 == 0 && $year % 100 != 0) {
    echo 'leap_year';
} elseif ($year % 400 == 0) {
    echo 'leap_year_too';
} else {
    echo 'not_leap_year';
}

//task 4
$i = 'abcde';
if ($i{0} == 'a') {
    echo 'yes';
} else {
    echo 'no';
}
   //task 5
$str = '512345';
if ($str{0}==1||$str==2||$str==3) {
	echo "true";
}
else{
	echo "false";}

// task 6
$i= array(1,2,3);
var_dump('i='.array_sum($i));