Hi!

Xdebug does not change the output of serialise. I've modified your script a little:

<?php

class Sleeper

{

private $data;

public function __construct($data)
{
    $this->data = $data;
}

public function __sleep()
{
    return ['data'];
}
}
echo serialize(new Sleeper("test")), "\n";

echo serialize(new Sleeper("\xC3\xA9")), "\n";

With Xdebug:

derick@singlemalt:~$ php /tmp/1822.php && php /tmp/1822.php | md5sum

O:7:"Sleeper":1:{s:13:"Sleeperdata";s:4:"test";}

O:7:"Sleeper":1:{s:13:"Sleeperdata";s:2:"é";}

f3015d04860932275a7e627d3ef5b4f2  -

Without Xdebug:

derick@singlemalt:~$ php -n /tmp/1822.php && php -n /tmp/1822.php | md5sum

O:7:"Sleeper":1:{s:13:"Sleeperdata";s:4:"test";}

O:7:"Sleeper":1:{s:13:"Sleeperdata";s:2:"é";}

f3015d04860932275a7e627d3ef5b4f2  -

The difference is purely in the output of xdebug's var_dump, where it escapes the \0 characters that are present in the original serialize() output:

derick@singlemalt:~$ php -n /tmp/1822.php | od -t x1

0000000 4f 3a 37 3a 22 53 6c 65 65 70 65 72 22 3a 31 3a

0000020 7b 73 3a 31 33 3a 22 00 53 6c 65 65 70 65 72 00

0000040 64 61 74 61 22 3b 73 3a 34 3a 22 74 65 73 74 22

0000060 3b 7d 0a 4f 3a 37 3a 22 53 6c 65 65 70 65 72 22

0000100 3a 31 3a 7b 73 3a 31 33 3a 22 00 53 6c 65 65 70

0000120 65 72 00 64 61 74 61 22 3b 73 3a 32 3a 22 c3 a9

0000140 22 3b 7d 0a

IMO, Xdebug does the right thing and instead outputs the \0 characters as "\000".

I see. Thanks for clarifying what's happening here!