simple PHP program

<?php
/* The Computer Language Benchmarks Game
   https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
   
   line-by-line from Greg Buchholz's C program
*/





$w = 0; $h = 0; $x = 0; $y = 0; $bit_num = 0;
$byte_acc = 0;
$i = 0; $iter = 50;
$limit = 2.0;
$Zr = 0; $Zi = 0; $Cr = 0; $Ci = 0; $Tr = 0; $Ti = 0;

$w = $argv[1];
$h = $w;

printf ("P4\n%d %d\n", $w, $h);

for ($y = 0 ; $y < $h ; $y++)
{
    for ($x = 0 ; $x < $w ; $x++)
    {
        $Zr = 0.0; $Zi = 0.0; 
        $Cr = (2.0 * $x / $w - 1.5); $Ci = (2.0 * $y / $h - 1.0);

        for ($i = 0 ; $i < $iter; $i++)
        {
            $Tr = $Zr*$Zr - $Zi*$Zi + $Cr;
            $Ti = 2*$Zr*$Zi + $Ci;  
            $Zr = $Tr; $Zi = $Ti;   
            if ($Zr*$Zr+$Zi*$Zi > $limit*$limit)
                break;
        }
    
        if($Zr*$Zr+$Zi*$Zi > $limit*$limit) 
            $byte_acc = ($byte_acc << 1) | 0x00;
        else
            $byte_acc = ($byte_acc << 1) | 0x01;
        
        $bit_num++; 

        if ($bit_num == 8)
        {
            echo chr ($byte_acc);
            $byte_acc = 0;
            $bit_num = 0;
        }
        else if ($x == $w - 1)
        {
            $byte_acc = $byte_acc << (8-$w%8);
            echo chr ($byte_acc);
            $byte_acc = 0;
            $bit_num = 0;
        }
        
    }
}
    

NOTES:
64-bit Ubuntu quad core
PHP 8.3.3 (cli)
(built: Mar  3 2024 08:47:21) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.3.3,
with Zend OPcache v8.3.3,
Copyright (c) Zend Technologies


 Sat, 09 Mar 2024 00:23:41 GMT

COMMAND LINE:
 /opt/src/php-8.3.3/bin/php -dzend_extension=/opt/src/php-8.3.3/lib/php/extensions/no-debug-non-zts-20230831/opcache.so -dopcache.enable_cli=1 -dopcache.jit_buffer_size=64M -n  simple.php 16000

(BINARY) PROGRAM OUTPUT NOT SHOWN