too simple PHP program

source code

<?php
/* The Computer Language Benchmarks Game
   https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
*/

$n = $argv[1];
$sum = 0.0;
$flip = -1.0;
for ($i = 1 ; $i <= $n ; $i++) {    
    $flip *= -1.0;        
    $sum += $flip / (2*$i - 1);  
}
printf("%0.9f\n", ($sum*4.0));

notes, command-line, and program output

NOTES:
64-bit Ubuntu quad core
PHP 8.3.7 (cli)
(built: May 28 2024 09:58:17) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.3.7,
with Zend OPcache v8.3.7,
Copyright (c) Zend Technologies


 Tue, 28 May 2024 19:57:18 GMT

COMMAND LINE:
 /opt/src/php-8.3.7/bin/php -dzend_extension=/opt/src/php-8.3.7/lib/php/extensions/no-debug-non-zts-20230831/opcache.so -dopcache.enable_cli=1 -dopcache.jit_buffer_size=64M -n  toosimple.php 10000000000

PROGRAM OUTPUT:
3.141592653