fork - simple fork for both Windows (with PowerShell) and Un*x (with Bash) in PHP. Returns PID.

fork.php

<?php

function fork($program, ...$args): int
{
    if (strtoupper(php_uname('s')) === 'WINDOWS NT') {
        $cmd = [
            'powershell.exe',
            '-Command',
            '$proc',
            '=',
            'Start-Process',
            escapeshellarg($program),
        ];
        if (count($args)) {
            $cmd[] = '-ArgumentList';
        }
        foreach ($args as $key => $arg) {
            $cmd[] = escapeshellarg($arg);
            if ($key < count($args) - 1) {
                $cmd[] = ',';
            }
        }
        $cmd = array_merge($cmd, [
            '-PassThru',
            ';',
            'echo',
            '$proc.id',
        ]);
    } else {
        $cmd = [
            escapeshellcmd($program)
        ];
        foreach ($args as $arg) {
            $cmd[] = escapeshellarg($arg);
        }
        $cmd = array_merge($cmd, [
            '>',
            '/dev/null',
            '2>',
            '/dev/null',
            '&',
            'echo',
            '$!',
        ]);
    }

    $command = implode(' ' , $cmd);
    exec($command, $output, $return);
    if ($return !== 0) {
        throw new RuntimeException("Failed starting $command");
    }
    if (!count($output)) {
        throw  new RuntimeException("Fatal error for $command");
    }
    return (int) $output[0];
}