PHP simulates two date processing functions of SQL Server_PHP tutorial

//It is very inconvenient to process dates in PHP. For example, find the month difference between two dates? What to do?
　 //File name: date.inc.php3
　 //Before using these two functions, you must first convert the date or date time into the timestamp type.
//For example:
//$today=mktime(0,0,0,date("m"),date("d"),date("Y"));
/* ***Simulate the dateadd function in sqlserver************
　$part type: string
Value range: year, month, day, hour, min, sec
　Represents: the date to be added Which part of
$n type: numeric value
Represents: how much to increase, which part to increase is determined according to $part
Can be a negative number
$datetime type: timestamp
Represents: the base of the increase
Return type: timestamp

******************End*******************/


function dateadd（$part,$n,$datetime）{
$year=date（"Y",$datetime）;
$month= date（"m",$datetime）;
$day=date（"d",$datetime）;
$hour=date（"H",$datetime）;
$min=date（ "i",$datetime);
$sec=date ("s",$datetime);
$part=strtolower ($part);
$ret=0;
switch ($ part) {
case "year":
$year+=$n;
break;
case "month":
$month+=$n;
break;
case "day":
$day+=$n;
break;
case "hour":
$hour+=$n;
break;
case "min":
$min+=$n;
break;
case "sec":
$sec+=$n;
break;
default:
return $ret;
break;
}
$ret=mktime($hour,$min,$sec,$month,$day,$year);
return $ret;
}

/****Simulate the datediff function in sqlserver************

$part type: string
Value range: year, month, day, hour, min, sec
Represents: To Which part of the date is added
$date1, $date2 Type: timestamp
Represents: two dates to be compared
Return type: numeric value

********* *****Finish*(*************/


function datediff($part,$date1,$date2){
//$diff=$date2-$date1;
$year1= date（"Y",$date1）;
$year2=date（"Y",$date2）;
$month2=date（"m",$date2）;
$month1=date（ "m",$date1);
$day2=date ("d",$date2);
$day1=date ("d",$date1);
$hour2=date ("d ",$date2);
$hour1=date ("d",$date1);
$min2=date ("i",$date2);
$min1=date ("i", $date1);
$sec2=date（"s",$date2）;
$sec1=date（"s",$date1）;

$part=strtolower（$part） ;
$ret=0;
switch ($part) {
case "year":
$ret=$year2-$year1;
break;
case "month" :
$ret=（$year2-$year1）*12+$month2-$month1;
break;
case "day":
$ret=（mktime（0,0,0 ,$month2,$day2,$year2)-mktime(0,0,0,$month1,$day1,$year1))/(3600*24);
break;
case "hour":
$ret=(mktime($hour2,0,0,$month2,$day2,$year2)-mktime($hour1,0,0,$month1,$day1,$year1))/3600;
break;
case "min":
$ret=（mktime（$hour2,$min2,0,$month2,$day2,$year2）-mktime（$hour1,$min1,0,$month1, $day1,$year1))/60;
break;
case "sec":
$ret=$date2-$date1;
break;
default:
return $ ret;
break;
}
return $ret;
}

}