How to imitate two date processing functions of SQLServer

// It is inconvenient to process dates in PHP, for example, to find the month with a different date? What should I do? // File name: date. inc. php3 // before applying the two functions, convert the date or date to the timestamp type. // For example: // $ today = // it is inconvenient to process the date in PHP. for example, it is inconvenient to calculate the month of the difference between two dates? What should I do?
// File name: date. inc. php3
// Before applying these two functions, convert the date or date to the timestamp type.
// For example:
// $ Today = mktime (0, 0, 0, date ('M'), date ('D'), date ('Y '));

/***** Mimic the dateadd function in sqlserver *******
$ Part Type: string
Value range: year, month, day, hour, min, sec
Performance: The part of the date to be added.
$ N type: value
Performance: determine which part to add based on $ part.
Negative
$ Datetime type: timestamp
Performance: increased base
Return type: timestamp
**************/
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;
}

/***** Mimic the datediff function in sqlserver *******
$ Part Type: string
Value range: year, month, day, hour, min, sec
Performance: The part of the date to be added.
$ Date1, $ date2 type: timestamp
Performance: two dates to be compared
Return type: numeric value
* ************** End *(*************/
Function datediff ($ part, $ date1, $ date2 ){
// $ Diff = $ date2-$ date1;
$ Year1 = date ('Y', $ date1 );
$ Year2 = date ('Y', $ date2 );
$ Mon2nd = 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 $ mon2s-$ month1;
Break;
Case 'day ':
$ Ret = (mktime (, 0, $ mon2, $ day2, $ year2)-mktime (, 0, $ month1, $ day1, $ year1 )) /(24x3600 );
Break;
Case 'hour ':
$ Ret = (mktime ($ hour2, $ mon2, $ day2, $ year2)-mktime ($ hour1, $ month1, $ day1, $ year1 )) /3600;
Break;
Case 'min ':
$ Ret = (mktime ($ hour2, $ min2, 0, $ mon2, $ day2, $ year2)-mktime ($ hour1, $ min1, 0, $ month1, $ day1, $ year1)/60;
Break;
Case 'SEC ':
$ Ret = $ date2-$ date1;
Break;
Default:
Return $ ret;
Break;
}
Return $ ret;
}

}