Bug #79030 [Nab]: $_SERVER['REQUEST_TIME_FLOAT'] and microtime(TRUE) combination problem

Edit report at https://bugs.php.net/bug.php?id=79030&edit=1 ID: 79030 User updated by: herbert at groot dot jebbink dot nl 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: 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. Previous Comments: ------------------------------------------------------------------------ [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