Working on a simple project, the objective is to find whether or not it is a leap year. In PHP, I attempted to use a ternary rather then the standard elseif statements.
$year = 2000;
$is_leapYear = ($year%400 == 0)? true: ($year%100 == 0)? false: ($year % 4 == 0);
echo ($year % 400 == 0) .'.'. ($year % 100 == 0) .'.'. ($year % 4 ==0);
echo $year . ' is ' . ($is_leapYear ? '' : 'not') . ' a leap year';
I discovered that this doesn't work because of a lack of parenthesis. Here is the correct solution:
$is_leapYear = ($year % 400 == 0)? true: (($year % 100 == 0)? false: ($year%4 == 0));
My question is why do ternary operators need parenthesis on the top true or false branch? I don't think the above code is ambiguous.
There's no need for such complicated code. PHP's date() can return whether it's a leap year or not:
$is_leap_year = (bool) date('L', mktime(0, 0, 0, 1, 1, $year));
See manual here.
There is no ambiguity and sadness of PHP Ternary Operator:
<?php
// on first glance, the following appears to output 'true'
echo (true?'true':false?'t':'f');
// however, the actual output of the above is 't'
// this is because ternary expressions are evaluated from left to right
// the following is a more obvious version of the same code as above
echo ((true ? 'true' : false) ? 't' : 'f');
// here, you can see that the first expression is evaluated to 'true', which
// in turn evaluates to (bool)true, thus returning the true branch of the
// second ternary expression.
?>
Your code executes like this:
$year = 2000;
$is_leapYear = (($year%400 == 0)? true: ($year%100 == 0)) ? false: ($year%4==0);
echo $is_leapYear;
LEFT-to-RIGHT