Use PHP's Strtotime () function cautiously, phpstrtotime function _php Tutorial

Use PHP's Strtotime () function sparingly, phpstrtotime function

We in the daily business, for the volume of business, often using the database by time to do horizontal sub-table, the query after the table will often involve time issues. For example, we would like to query a user's order for 1 months from the current time, at which point some of us would use the Strtotime () function to handle it.

But using Strtotime () requires a lot of caution. Let's look at a piece of code, the code is intended to get months of the year, for example, today is August 1, 2014, I want to get 2 months ago the year month is an array ("0" = "201406", "1" and "201407",)

1 /****2 * $mthNum a few months ago3 * return like array (' 0 ' = ' 201401 ', ' 1 ' = ' 201402 '), the result does not contain the current month4 ************/5 functionGettimeym ($mthNum)6 {7     $TIMEARR=Array();8     9     if($mthNum<= 0)Ten         return $TIMEARR; One  A      Do  -     { -         $TIMEARR[] =Date("Ym",Strtotime("-$mthNumMonth)); the         $mthNum--; -     } -      while($mthNum> 0); -  +     return $TIMEARR; -}

　　

The surface look at the code seems to be no problem, but we do a test, the following is the test code, the purpose of the test is very simple, just want to test, the last day of the month the first one months of the date is how much

1 
 Php2 $DATEARR=Array(3"2014-01-31 00:00:00-1 Month",4"2014-02-28 00:00:00-1 Month",5"2014-03-31 00:00:00-1 Month",6"2014-04-30 00:00:00-1 Month",7"2014-05-31 00:00:00-1 Month",8"2014-06-30 00:00:00-1 Month",9"2014-07-31 00:00:00-1 Month",Ten"2014-08-31 00:00:00-1 Month", One"2014-09-30 00:00:00-1 Month", A"2014-10-31 00:00:00-1 Month", -"2014-11-30 00:00:00-1 Month", -"2014-12-31 00:00:00-1 Month", the ); -  - foreach($DATEARR  as $val) - { +     $time=Strtotime($val); -     Echo[$time][$val]." \ r \ n "; +}

Let's take a look at the test results, and from the test results we've found that we're ignoring the difference in the number of days per month , so Strtotime () results in a different result.

So what exactly is Strtotime ("-$n month") calculated? Do a test as follows: Look at the results

1 
 Php2 3 $testTime=Date("Y-m-d h:i:s", Time());4 Echo"Test time: {$testTime} \ r \ n ";5 6 $flag= 0; 7 $time= 0;8 $tmp= 0;9 Ten  while(1) One { A     if($flag+ > 12) -          Break; -  the     $time=Strtotime("-$flagMonth); -     $monthDiff= ($time-$tmp)/86400;//86400 = * *, -     $tmp=$time; -  +     $dispDate=Date("Y-m-d h:i:s",$time); -  +     Echo"{$flag} month ago: {$time}, Date: {$dispDate)} Difference Value: {$dispDate} days \ r \ n "; A}

(Note: Strtotime ("-$n Month"), the second parameter is omitted, the second parameter represents the time of the distance, the ellipsis represents the current time)

time	Difference	Theoretical time	results
July 31	January ago	June 31	June only 30 days, then add one day to July 1
July 31	February ago	May 31
July 31	March ago	April 31	April only 30 days, then add one day to May 1
...

So if so, how do we use Strtotime ("-$n month") to deal with our needs?

Here is a handwritten code for reference

1 /****************2 * Resolve the two time period between the month3 * $btm, $etm is a UNIX timestamp4 *****************/5 functionGettimedis ($BTM,$etm)6 {7     $RESARR=Array();8     if($etm<$BTM)9         return $RESARR;Ten  One     //turn both BTM and Etm to 1th per month . A     $BTMC=Strtotime(Date("Y-m-01 00:00:00",$BTM)); -     $ETMC=Strtotime(Date("Y-m-01 00:00:00",$etm)); -  the  -     $flag= 0;//Time Difference identifier -     $RESARR[] =Date("Ym",$ETMC); -  +      while(1) -     { +         $flag++; A         $compTime=Strtotime("-{$flag} month ",$ETMC); at          -         if($compTime<$BTM) -              Break; -  -         $RESARR[] =Date("Ym",$compTime); -     } in  -     return Array_unique($RESARR); to}

Problems with strtotime functions in PHP

Mktime () requires a parameter.

The simplest way to get two days is:

echo Date ("Y-m-d", Strtotime ("+2 Days"));
Echo '
';
echo Date ("Y-m-d h:i:s", Strtotime ("+2 Days"));
?>
Take a good look at Strtotime's function description, you can also
+10 hours
-2 hours
Wait a minute.

How does the PHP strtotime function change at a specified time?

$date = Date ("y-m-d", Strtotime (' 2012-01-20 ') + 60*60*24);

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