PHP无法选择单选按钮值

im trying to get the value from radio button which was selected among other radio buttons. This is basically a calendar of month.

This is how i try to select the value.

$radio_value = $_POST['day'];
if(isset($_POST['get_value'])) {
for($i=1;$i<=$number;$i++) {
    if($radio_value == $i) {
    $_SESSION["value"] = $radio_value;
    }
}
}

This is how i create 30 radio buttons the $i variable is just for loop.

echo '<td><input name="day" type="radio" value="' . $i . '">' .$i.  '</td>';

All other html php related things work so this is the only problem.

EDIT html form. form method is set to post and action is the php file so no problem here either.

<input type="submit" name="get_value" value="Patvirtinti">&nbsp;&  nbsp;&nbsp;&nbsp;
<input type="submit" name="valyti_forma" value="Valyti forma">

I will try to explain this so you can understand. I get $number value from cal_days_in_month. When i have the $number then i run a loop to create as many radio buttons as the value is. And then when i click the radio button and press my submit button i want to print that radio button value which is 1,2,3 etc(its a day in a month). Hope this is clear enough.