2가지 중에서 eval_decode가 좀더 정확.

<?php
/*
 * Basic script to decrypt files encoded with eval(gzinflate(base64_decode($data)));
 */

$file = 'proc.php';
$content = file_get_contents($file);

function eval_decode($content, $step = 0)
{
    $content = preg_replace('/\s*<\?php/', '', $content);

    $pattern = '/eval\s*\(/';
    $step++;
    if (preg_match($pattern, $content)) {
        $content = preg_replace($pattern, 'print(', $content);
        ob_start();
        eval($content);
        $content = ob_get_contents();
        ob_end_clean();
    }
    $content = trim($content);
    if (preg_match($pattern, $content)) {
        $content = eval_decode($content, $step);
    }

    return $content;
}

function evaldecode($content, $step = 0) {
    //echo "STEP $step\n";
    $step++;
    if(preg_match('/^eval\(/', $content)) {
        $content = str_replace('eval(', 'print(', $content);

        ob_start();
        eval($content);
        $content = ob_get_contents();
        ob_end_clean();
    }

    $content = trim($content);
    if(preg_match('/^eval\(/', $content)) {
        $content = evaldecode($content, $step);
    }

    return $content;
}

echo evaldecode($content)."\n";

echo eval_decode($content)."\n";

https://gist.github.com/yireo/f9e3ba3b7e8cca7d74c3