sqlserver2000 Personal Edition simulates two functions of SQLSERVER: dateadd, datediff

//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: which part of the date to be added
$n Type: Numeric
Represents: How much to increase, which part to add is decided based on $part
Can be a negative number
$datetime type: timestamp
Represents: the base of the increase
Return type: timestamp
*********** ***Finish**************/
function dateadd($part,$n,$datetime){
$year=date("Y",$datetime);
$m>$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: which part of the date to add
$date1 ,$date2 Type: timestamp
Represents: two dates to be compared
Return type: numerical value
**************End*(*************/
function datediff($part,$date1,$date2){
//$diff=$date2-$date1;
$year1=date("Y",$date1);
$year2=date("Y",$date2);
$m>$m>$day2=date("d",$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;
}
?>

The above introduces the two functions of sqlserver2000 Personal Edition that simulate SQLSERVER: dateadd and datediff, including the content of sqlserver2000 Personal Edition. I hope it will be helpful to friends who are interested in PHP tutorials.