How to determine leap year in php? Introduction to three methods

Leap year refers to a leap year every four years in the Gregorian calendar, that is, a year with 366 days inserted between ordinary 365-day years. Its purpose is to match the solar year.

According to the provisions of the Gregorian calendar, there are generally two situations in leap years: ① The year is evenly divisible by 4, but not 100; ② The year is evenly divisible by 400. In this article, we will introduce to you the method of realizing leap year judgment based on PHP programming language.

1. Use if statement to determine leap year

The if statement is a very common control statement in PHP, which is determined by logically judging the conditions. Determine the branch direction of the program. The following is the code that uses if statements to determine leap years:

function isLeapYear($year)
{
    $isLeap = false;

    if ($year % 4 == 0) {
        $isLeap = true;
        if ($year % 100 == 0 && $year % 400 != 0) {
            $isLeap = false;
        }
    }

    return $isLeap;
}

In the above code, we use the variable $isLeap to store the true and false values ​​​​of leap years. First determine whether $year is divisible by 4. If so, set $isLeap to true. Next, determine whether $year is divisible by 100. If so, according to the definition of leap year, it needs to be divisible by 400 to determine whether it is a leap year. Otherwise, set $isLeap to false. Finally, the value of $isLeap is returned.

2. Use the ternary operator to simplify the code

The ternary operator (?:) is a very concise syntax that can The if-else statement is reduced to one line of code. The following is the code that uses the ternary operator to realize leap year judgment:

function isLeapYear($year)
{
    return ($year % 4 == 0 && ($year % 100 != 0 || $year % 400 == 0));
}

In the above code, we set the return value directly to the judgment result and use the ternary operator to judge the condition. If $year is divisible by 4, not divisible by 100, or divisible by 400, then return true, otherwise return false.

It should be noted that using the ternary operator can make the code more concise, but for beginners, this syntax may not be easy to understand. It is recommended to learn it after mastering the if statement.

3. Use switch statement to realize leap year judgment

In addition to if statement and ternary operator, we can also use switch statement to realize leap year judgment judge. The following is the code that uses the switch statement to implement leap year judgment:

function isLeapYear($year)
{
    switch (true) {
        case ($year % 400 == 0):
            return true;
        case ($year % 100 == 0):
            return false;
        case ($year % 4 == 0):
            return true;
        default:
            return false;
    }
}

In the above code, we use the switch statement to judge $year and execute different branch codes for different situations. If $year is divisible by 400, it returns true; if $year is divisible by 100, it returns false; if $year is divisible by 4, it returns true; if none of the above conditions are met, it returns false.

Summary

Among the above three methods, the if statement is the most commonly used method and the easiest to understand. The ternary operator can make the code more concise, but it needs to be learned based on mastering the if statement. Although the switch statement is not commonly used in leap year judgment, it may be used in other scenarios, so it needs to be learned and mastered.

Finally, I hope this article can help readers understand the method of realizing leap year judgment in PHP and be able to apply it in actual development.

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