PHP emulates SQL Server two date processing functions _php basics

Processing dates in PHP is very inconvenient, such as asking for a difference between the two dates of the month? What should we do?
FileName: date.inc.php3
Before you use these two functions, you must first convert the date or datetime to the timestamp type.
Such as:
$today =mktime (0,0,0,date ("M"), Date ("D"), Date ("Y"));
/**** simulate the DATEADD function in SQL Server *******
$part Type: string
Value range: year,month,day,hour,min,sec
Which part of the date to increase
$n Type: Numeric value
said: To increase how much, according to $part decide which part to add
Can be a negative number
$datetime Type: Timestamp
Indicated: increased cardinality
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 SQL Server *******

$part Type: string
Value range: year,month,day,hour,min,sec
Which part of the date to increase
$date 1, $date 2 type: Timestamp
Indicates: two dates to compare
Return type: Numeric value

End * (*************/


function DateDiff ($part, $date 1, $date 2) {
$diff = $date 2-$date 1;
$year 1=date ("Y", $date 1);
$year 2=date ("Y", $date 2);
$month 2=date ("M", $date 2);
$month 1=date ("M", $date 1);
$day 2=date ("D", $date 2);
$day 1=date ("D", $date 1);
$hour 2=date ("D", $date 2);
$hour 1=date ("D", $date 1);
$min 2=date ("i", $date 2);
$min 1=date ("i", $date 1);
$sec 2=date ("s", $date 2);
$sec 1=date ("s", $date 1);

$part =strtolower ($part);
$ret = 0;
Switch ($part) {
Case "Year":
$ret = $year 2-$year 1;
Break
Case "Month":
$ret = ($year 2-$year 1) *12+ $month 2-$month 1;
Break
Case ' Day ':
$ret = (Mktime (0,0,0, $month 2, $day 2, $year 2)-mktime (0,0,0, $month 1, $day 1, $year 1))/(3600*24);
Break
Case "Hour":
$ret = (Mktime ($hour 2,0,0, $month 2, $day 2, $year 2)-mktime ($hour 1,0,0, $month 1, $day 1, $year 1))/3600;
Break
Case "min":
$ret = (Mktime ($hour 2, $min 2,0, $month 2, $day 2, $year 2)-mktime ($hour 1, $min 1,0, $month 1, $day 1, $year 1))/60;
Break
Case "SEC":
$ret = $date 2-$date 1;
Break
Default
return $ret;
Break
}
return $ret;
}

}