Description:
------------
I'd like to know if it's reasonable to have 'implode' function do not concatenate 'null/false' values into resulting string.

like it does 'http_build_query' (http://php.net/http_build_query)



Reproduce code:
---------------
<?php
$dirs		=  array(
'dir1',
'dir2',
false,
'dir3'
);

$dir_str    = implode( DIRECTORY_SEPARATOR, $dirs);
echo $dir_str; 
?>

Expected result:
----------------
dir1\dir2\dir3

Actual result:
--------------
dir1\dir2\\dir3