php正则对\\\\转义的特殊处理需要注意

<?php
echo preg_replace("/[^\/\-\w\.\\]/", '', 'dd\\\/dd');


提示出错
Warning: preg_replace() [function.preg-replace]: Compilation failed: missing terminating ] for character class at offset 12 in G:\www\test\index.php on line 2
 
<?php
echo preg_replace("/[^\/\-\w\.\\\]/", '', 'dd\\\/dd');dd\\/dd
<?php
echo preg_replace("/[^\/\-\w\.\\\\]/", '', 'dd\\\/dd');dd\\/dd

好像是挨消耗掉一条