mktime

localtime

Last updated: Fri, 25 Jul 2008

microtime

(PHP 4, PHP 5)

microtime — Return current Unix timestamp with microseconds

Description

mixed microtime ([ bool $get_as_float ] )

microtime() returns the current Unix timestamp with microseconds. This function is only available on operating systems that support the gettimeofday() system call.

Parameters

get_as_float

When called without the optional argument, this function returns the string "msec sec" where sec is the current time measured in the number of seconds since the Unix Epoch (0:00:00 January 1, 1970 GMT), and msec is the microseconds part. Both portions of the string are returned in units of seconds.

If the optional get_as_float is set to TRUE then a float (in seconds) is returned.

ChangeLog

Version	Description
5.0.0	The `get_as_float` parameter was added.

Examples

Example #1 Timing script execution with microtime()


<?php
/**
 * Simple function to replicate PHP 5 behaviour
 */
function microtime_float()
{
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
}

$time_start = microtime_float();

// Sleep for a while
usleep(100);

$time_end = microtime_float();
$time = $time_end - $time_start;

echo "Did nothing in $time seconds\n";
?>

Example #2 Timing script execution in PHP 5


<?php
$time_start = microtime(true);

// Sleep for a while
usleep(100);

$time_end = microtime(true);
$time = $time_end - $time_start;

echo "Did nothing in $time seconds\n";
?>


I wanted to find out whether echo would be quicker in small chunks or one large chunk to test the theory mentioned in the previous post.  The following experiment shows that there is no significant performance difference, in terms of execution time elapsed, between the two methods of using echo.  I ran two test cases, one with a string that is 100000 bytes long and another with a string length of 1000000.  The source code follows below.



<?php



function echobig($string, $bufferSize = 8192)

{

    $splitString = str_split($string, $bufferSize);



    foreach($splitString as $chunk)

        echo $chunk;

}



global $dat;

$dat = "";



function testit()

{

global $dat;

$data = "";



for( $a = 0; $a <= 1000000; $a += 1 ) $data .= "a";



$u1= microtime(true);

echobig( $data );

$u2= microtime(true);

echo $data;

$u3= microtime(true);



$diff = $u2 - $u1;

$diff2= $u3 - $u2;

$dat .= "$diff2 $diff    $u2  $u1\r\n";

}



$i = 0;

while( $i < 5 )

{

  testit(); $i += 1;

}



global $dat;

$fp = fopen( "../Data/results.txt", "w" );

fwrite( $fp, $dat );

fclose( $fp );

?>



You can run the above experiment yourself or you can look at my test data.  I got some test data here:  http://www.codesplunk.com/examples/echo.html

kpsimoulis [at] genatec
05-Jun-2008 12:53


This function is very useful for putting a start and end point in your page to find out where is the delay.



<?php



$start = microtime(true);

// My source code here

$end = microtime(true);



echo $end."-".$start."=".($end - $start). " seconds";



?>



If you try this example above (without any source code between the start and the end point). You will get an ugly value, something like:

1212690530.4132-1212690530.4132=8.1062316894531E-6 seconds



You will wonder why you get this because both numbers seem to be equal. Well this is because there is a hidden precision that we are not able to see.



To solve this problem I made a new function:



<?php



function my_microtime($precision = 4)

{

    return round(microtime(true),4);

}



$start = microtime(true);

// My source code here

$end = microtime(true);



echo $end."-".$start."=".substr(($end - $start),0,5). " seconds";



?>



It would be useful if they add another parameter for precision in this function or at least another boolean that will not include the hidden precision.

You can read more about the hidden precision in http://php.net/float

Peter Kehl
30-May-2008 03:31


This function allows you to easily calculate time difference between two points in time without losing the precision.





<?php





    /**    Calculate a precise time difference.


        @param string $start result of microtime()


        @param string $end result of microtime(); if NULL/FALSE/0/'' then it's now


        @return flat difference in seconds, calculated with minimum precision loss


    */


    function microtime_diff( $start, $end=NULL ) {


        if( !$end ) {


            $end= microtime();


        }


        list($start_usec, $start_sec) = explode(" ", $start);


        list($end_usec, $end_sec) = explode(" ", $end);


        $diff_sec= intval($end_sec) - intval($start_sec);


        $diff_usec= floatval($end_usec) - floatval($start_usec);


        return floatval( $diff_sec ) + $diff_usec;


    }





?>

luke at lucanos dot com
28-May-2008 04:48


Rather than using the list() function, etc. I have found the following code to be a bit cleaner and simpler:

<?php

$theTime = array_sum( explode( ' ' , microtime() ) );

echo $theTime;

# Displays "1212018372.3366"

?>

admin at emuxperts dot net
20-Aug-2006 07:37


This little function comes in handy if you want a single integer when your server doesn't have php >= 5.0



It returns seconds passed unix epoch to the microsecond. Or microseconds since unix epoch.



<?php

//A hack for PHP < 5.0

function utime($inms){

    $utime = preg_match("/^(.*?) (.*?)$/", microtime(), $match);

    $utime = $match[2] + $match[1];

    if($inms){

        $utime *=  1000000;

    }

    return $utime;

}



//Example:

print utime();

//Returns:

//1156127104.746352 Seconds



//Example two:

print utime(1);

//Returns:

//1156127104746352 Microseconds

?>

EdorFaus
16-May-2006 12:47


Of the methods I've seen here, and thought up myself, to convert microtime() output into a numerical value, the microtime_float() one shown in the documentation proper(using explode,list,float,+) is the slowest in terms of runtime.



I implemented the various methods, ran each in a tight loop 1,000,000 times, and compared runtimes (and output). I did this 10 times to make sure there wasn't a problem of other things putting a load spike on the server. I'll admit I didn't take into account martijn at vanderlee dot com's comments on testing accuracy, but as I figured the looping code etc would be the same, and this was only meant as a relative comparison, it should not be necessary.



The above method took on average 5.7151877 seconds, while a method using substr and simply adding strings with . took on average 3.0144226 seconds. rsalazar at innox dot com dot mx's method using preg_replace used on average 4.1819633 seconds. This shows that there are indeed differences, but for normal use noone is going to notice it.



Note that the substr method mentioned isn't quite the one given anonymously below, but one I made based on it:

<?php

$time=microtime();

$timeval=substr($time,11).substr($time,1,9);

?>



Also worth noting is that the microtime_float() method gets faster, and no less accurate, if the (float) conversions are taken out and the variables are simply added together.



Any of the methods that used + or array_sum ended up rounding the result to 2 digits after the decimal point, while (most of) the ones using preg_replace or substr and . kept all the digits.



For accurate timing, since floating-point arithmetic would lose precision, I stored microtime results as-is and calculated time difference with this function:

<?php

function microtime_used($before,$after) {

    return (substr($after,11)-substr($before,11))

        +(substr($after,0,9)-substr($before,0,9));

}

?>



For further information, the script itself, etc, see http://edorfaus.xepher.net/div/convert-method-test.php

Z0d
13-Feb-2006 07:03


The shortest way for PHP4 users really is



$ts = strtok(microtime(), ' ') + strtok('');

radek at pinkbike com
24-Nov-2005 08:48


A lot of the comments here suggest adding in the following way:  (float)$usec + (float)$sec

Make sure you have the float precision high enough as with the default precision of 12, you are only precise to the 0.01 seconds.  

Set this in you php.ini file.

        precision    =  16

vladson at pc-labs dot info
19-Jun-2005 03:49


I like to use bcmath for it

<?php

function micro_time() {

    $temp = explode(" ", microtime());

    return bcadd($temp[0], $temp[1], 6);

}



$time_start = micro_time();

sleep(1);

$time_stop = micro_time();



$time_overall = bcsub($time_stop, $time_start, 6);

echo "Execution time - $time_overall Seconds";

?>

php at washboardabs dot net
24-Feb-2005 12:57


Interesting quirk (tested in PHP 5.0.3): You can get very wacky results from microtime when it is called in the destructor of an object at the end of a script. These times vary enormously and can be in the *past*, when compared to microtime calls in the body of the script.



As a case example, I played with a timer object that measured microtime when it was created at the start of the script, and measured microtime again at the end of the script using __destruct(); and then printed the total execution time (end time - start time) at the bottom of the page. On short scripts, this would often give a negative time!



This quirk does not appear if microtime is measured with an automatic shutdown function (using <?PHP register_shutdown_function('myfunc') ?>. Incidentally, the automatic shutdown functions are called after output buffers are flushed but before object destructors are called.

mcq at supergamez dot hu
11-Dec-2000 10:47


if you want to measure runtime of some code, and the result is really relevant, then keep in mind the followings:


1. you should only measure the time the code runs. This means if you use functions to make a double from microtime, then get begin time, run the code, get end time, and only _after_ this do conversion and computing. This is relevant for short cycles.


2. if runtime is very small, you can put the code in a loop and run it for 100 or 1000 times. The more you run it the more accurate the value will be. Do not forget to divide the runtime by the times you ran it.


3. if you are measuring a loop, then you do not actually measure the runtime of one cycle. Some caching may occur which means you will not get one cycle's runtime. For a short code, this can eventually result in big differences. Use looping only if the code is long and comlicated.


4. your runtime will be highly affected by the load of the server, which may be effected by many things - so, always run your runtime measuering multiple times, and, when comparing two methods, for e.g., then measure their runtimes one after the other, so I mean do not use values from yesterday, the circumstances may strongly affect your measuring.





Trapeer

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