LOCK_NB is actually supported on windows as well. The only thing that currently doesn't work is the $wouldblock by ref param.

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@335862 c90b9560-bf6c-de11-be94-00142212c4b1

reference/filesystem/functions/flock.xml

@@ -28,8 +28,7 @@
    PHP supports a portable way of locking complete files in an advisory way
    (which means all accessing programs have to use the same way of locking
    or it will not work). By default, this function will block until the
-   requested lock is acquired; this may be controlled (on non-Windows
-   platforms) with the <constant>LOCK_NB</constant> option documented below.
+   requested lock is acquired; this may be controlled with the <constant>LOCK_NB</constant> option documented below.
   </para>
  </refsect1>
  
@@ -69,7 +68,7 @@
       <para>
        It is also possible to add <constant>LOCK_NB</constant> as a bitmask to one 
        of the above operations if you don't want <function>flock</function> to 
-       block while locking. (not supported on Windows)
+       block while locking.
       </para>
      </listitem>
     </varlistentry>