Edit report at https://bugs.php.net/bug.php?id=79030&edit=1
ID: 79030
Updated by: requinix@php.net
Reported by: herbert at groot dot jebbink dot nl
Summary: $_SERVER['REQUEST_TIME_FLOAT'] and microtime(TRUE)
combination problem
Status: Not a bug
Type: Bug
Package: *General Issues
Operating System: ChromeOS / Crostini / Debian 10
PHP Version: 7.4.1
Block user comment: N
Private report: N
New Comment:
REQUEST_TIME_FLOAT is not rounded.
To make sure, what SAPI are you using for the web side? One can define its own means of determining
the request time, and if it does not then PHP falls back to gettimeofday.
https://github.com/php/php-src/blob/PHP-7.4.1/main/SAPI.c#L1083
Previous Comments:
------------------------------------------------------------------------
[2019-12-26 06:00:31] herbert at groot dot jebbink dot nl
gettimeofday(2) may not be accurate at sub-millisecond level, but with 2 sequential calls the last
one will not be lower then the first one.
I think it is caused by the fact that $_SERVER['REQUEST_TIME_FLOAT'] is rounded to
milliseconds and microtime(TRUE) is not.
------------------------------------------------------------------------
[2019-12-25 09:12:46] requinix@php.net
Those two are backed by gettimeofday(2), which is not suitable for measuring time intervals to
sub-millisecond precision.
------------------------------------------------------------------------
[2019-12-25 06:56:21] herbert at groot dot jebbink dot nl
Description:
------------
Sometimes the $_SERVER['REQUEST_TIME_FLOAT'] and microtime(TRUE) combination gives strange
results.
Below example gives about 1 in 10 times a negative result.
Test script:
---------------
<?php
$script1 = microtime(TRUE);
$script2 = file_get_contents('http://localhost/script2.php');
echo $script2 - $script1;
?>
<?php
echo $_SERVER['REQUEST_TIME_FLOAT'];
?>
Expected result:
----------------
0.00038409233093262
Actual result:
--------------
-0.00039100646972656
------------------------------------------------------------------------
--
Edit this bug report at https://bugs.php.net/bug.php?id=79030&edit=1