Description:
------------
A string containing "\0" passed into error_log() causes the message to be 
truncated after that character. This is especially apparent when a log message 
contains a serialized object which has private properties, as their serialization 
key is \0classname\0propname.

file_put_contents is not affected, nor is using error_log with the destination 
parameter; only when using the ini setting.

Digging around through source, it looks like it's caused by the use of c strlen() 
in xbuf_format_converter (main/spprintf.c:576) which assumes null-terminated 
strings, called by vspprintf() -> ssprintf() -> php_log_err()

Happens in 5.4.x as well as a just-built git master 5.6.0-dev

Test script:
---------------
<?php

class a {
	private $b = 'c';
}
$obj = new a;
$str = serialize($obj);

ini_set('error_log', '/Users/eric/Desktop/error_log.log');
error_log($str); // truncated
file_put_contents('/Users/eric/Desktop/fpc.log', $str); // ok
error_log($str, 3, '/Users/eric/Desktop/error_log_param.log'); // ok

Expected result:
----------------
All three files should contain the following string:

O:1:"a":1:{s:4:"ab";s:1:"c";}

(note that "ab" is actually "\0a\0b")

Hex dump:
4F 3A 31 3A 22 61 22 3A 31 3A 7B 73 3A 34 3A 22 00 61 00 62 22 3B 73 3A 31 3A 22 
63 22 3B 7D

Actual result:
--------------
error_log.log contains only the following:

[16-Mar-2013 04:23:06 UTC] O:1:"a":1:{s:4:"

(the timestamp is not relevant)
4F 3A 31 3A 22 61 22 3A 31 3A 7B 73 3A 34 3A 22 0A

The other two files (error_log_param.log, fpc.log) correctly record the full 
string.