microtime(true) is 10x faster than microtime()

gistfile1.txt

➜  phpstan-src git:(pr/6378) ✗ php -v                      
PHP 8.5.10 (cli) (built: Aug 25 2026 21:09:32) (NTS)
Copyright (c) The PHP Group
Built by Homebrew
Zend Engine v4.5.10, Copyright (c) Zend Technologies
    with Zend OPcache v8.5.10, Copyright (c), by Zend Technologies

➜  phpstan-src git:(pr/6378) ✗ php test.php # hrtime();   
string(9) "1,826,708"
➜  phpstan-src git:(pr/6378) ✗ php test.php # hrtime();
string(9) "1,837,125"
➜  phpstan-src git:(pr/6378) ✗ php test.php # hrtime();
string(9) "1,864,667"
➜  phpstan-src git:(pr/6378) ✗ php test.php # hrtime(true);
string(9) "1,131,542"
➜  phpstan-src git:(pr/6378) ✗ php test.php # hrtime(true);
string(9) "1,133,125"
➜  phpstan-src git:(pr/6378) ✗ php test.php # hrtime(true);
string(9) "1,089,583"
➜  phpstan-src git:(pr/6378) ✗ php test.php # microtime(true);                         
string(9) "1,838,334"
➜  phpstan-src git:(pr/6378) ✗ php test.php # microtime(true);
string(9) "1,799,500"
➜  phpstan-src git:(pr/6378) ✗ php test.php # microtime();    
string(10) "12,017,250"
➜  phpstan-src git:(pr/6378) ✗ php test.php # microtime();
string(10) "12,343,250"
➜  phpstan-src git:(pr/6378) ✗ cat test.php                               
<?php

$start = hrtime(true);
for ($i=0; $i < 100000;$i++) {
        microtime();
}
var_dump(number_format(hrtime(true)-$start));