How to determine the number of days in a specified month through PHP

In the previous article "php loop learning ten: determine the number of narcissus, print the number of all narcissus", we introduced the determination of the number of narcissus, and use the for loop to output the number of all narcissus Methods. This time we will take a look at date and time and introduce how to use PHP to get the maximum number of days in a certain year or month.

The theme of this article is: given a year and month, determine how many days there are in the month.

We all know that the maximum number of days in a month is divided into 4 situations:

• Big month: 31 days;
  

• Small month: 30 days;

• February in leap year: 29 days
  

• February in ordinary year: 28 days

Every year, January, March, May, July, August, October and December are fixed as big months, while April, June, September and November are small months.

So we can use the selection control statement switch case to make a judgment selection:

When the month$month is 1, 3, 5, 7, 8, 10, and 12 will output 31; when $month is 4, 6, 9, and 11, 30 will be output. The code can be written like this:

switch($month){
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
	echo "$month 月共有31天";break;
case 4:
case 6:
case 9:
case 11:
	echo "$month 月共有30天";break;
}

Test it:

When $month=1, it will output:

When$month=4, it will output:

Explanation: The switch statement will be based on the expression The value is compared with the value in the case in turn. If they are not equal, continue to search for the next case; if they are equal, the corresponding statement will be executed until the switch statement ends or a break is encountered.

OK, the judgment of big and small months is still very simple. There is only one month of February left. To calculate the number of days in February, you first need to judge whether the year is a leap year. We can use the following function to achieve this: (For details, you can read the article "How PHP outputs all leap years in the 20th century")

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

If the given year is a leap year, it will return true or 1 , if it is not a leap year (it is an ordinary year), it returns false or 0.

Then call the IsLeapYear($year) function in the switch case statement to make the judgment:

case 2:
	echo IsLeapYear($year)? "$month 月共有29天" : "$month 月共有28天";break;

Ternary operator

表达式1?表达式2:表达式3

Copy after login

means: if the condition "Expression 1" is true, execute the statement "Expression 2", otherwise execute "Expression 3".

We can also add a default branch to remind the user when entering a number other than 1 to 12 months:

default:echo '输入错误，请输入1-12之间的数';break;

Okay, encapsulate the above code as A functional function:

function IsLeapYear($year){
   return ($year % 400 == 0 || $year % 4 == 0 && $year % 100 != 0);
}
function GetMaxDay($year,$month)
{
	switch($month){
	case 1:
	case 3:
	case 5:
	case 7:
	case 8:
	case 10:
	case 12:
		echo "$year 年 $month 月共有31天
";break;
	case 4:
	case 6:
	case 9:
	case 11:
		echo "$year 年 $month 月共有30天
";break;
	case 2:
		echo IsLeapYear($year)? "$year 年  $month 月共有29天
" : "$year 年  $month 月共有28天
";break;
	default:echo '输入错误，请输入1-12之间的数
';break;
	}
}

Call GetMaxDay($year,$month)Function:

GetMaxDay(2000,2);
GetMaxDay(2001,2);
GetMaxDay(2001,3);
GetMaxDay(2001,4);

Let’s take a look at the output result:

It can be seen that because 2000 is a leap year, there are 29 days in February; 2001 is an ordinary year, so there are 29 days in February. March is a big month, so it has 31 days; April is a small month, so it has 30 days.

Okay, that’s all. If you want to know anything else, you can click this. → →php video tutorial

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