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Bug #75098 Unexpected output
Submitted: 2017-08-20 07:31 UTC Modified: 2017-08-22 05:52 UTC
From: coolbalyan at gmail dot com Assigned:
Status: Not a bug Package: *General Issues
PHP Version: 7.1.8 OS: window,ubuntu
Private report: No CVE-ID: None
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 [2017-08-20 07:31 UTC] coolbalyan at gmail dot com 
Description:
------------
When script subtract value from two "microtime", it produce value in unexpected way. script take almost a fraction on second but substraction of value from taken from "microtime" make it incremented. it looks like it taking near around 9-10 seconds.

Test script:
---------------
$time_start=microtime(TRUE);


/****Performance Check****/
$time_end=microtime(TRUE);
var_dump(PHP_VERSION, $time_end-$time_start);



Expected result:
----------------
0

Actual result:
--------------
9.5367431640625E-7

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 [2017-08-20 07:49 UTC] requinix@php.net
-Status: Open +Status: Not a bug
 [2017-08-20 07:49 UTC] requinix@php.net 
Floating point values have a limited precision. Hence a value might 
not have the same string representation after any processing. That also
includes writing a floating point value in your script and directly 
printing it without any mathematical operations.

If you would like to know more about "floats" and what IEEE
754 is, read this:
http://www.floating-point-gui.de/

Thank you for your interest in PHP.

> it looks like it taking near around 9-10 seconds.
https://en.wikipedia.org/wiki/Scientific_notation#E-notation
 [2017-08-22 04:58 UTC] coolbalyan at gmail dot com
-Operating System: window +Operating System: window,ubuntu
 [2017-08-22 04:58 UTC] coolbalyan at gmail dot com 
If you run the test script, it actually produces that result without taking 9 seconds. That's odd, the script holding only 

$time_start=microtime(TRUE);


/****Performance Check****/
$time_end=microtime(TRUE);
var_dump(PHP_VERSION, $time_end-$time_start);

I actually rerun it in PHP 5.6.20 and 7.1.6 it returns float(0) but in 7.1.8 and 7.0.22 it returns higher values.
 [2017-08-22 05:14 UTC] spam2 at rhsoft dot net 
what about reading the links you got already provided - it does NOT take 9 seconds notice the E-7 which means "move the comma 7 positions left"
 [2017-08-22 05:52 UTC] coolbalyan at gmail dot com 
Thanks, not a bug
 
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