靶场php的特性，php特性

<?php highlight_file(__FILE__); include("ctfshow.php"); //flag in class ctfshow; $ctfshow = new ctfshow(); $v1 = $_GET['v1']; $v2 = $_GET['v2']; $v3 = $_GET['v3']; $v0 = is_numeric($v1) and is_numeric($v2) and is_numeric($v3); if ($v0) { if (!preg_match("/\;/", $v2)) { if (preg_match("/\;/", $v3)) { eval("$v2('ctfshow')$v3"); } } }