Description:
------------
The touch() function truncates the file if it is a "large file" (i.e. larger than 2GB).

Current PHP touch() implementation uses stat() to test if the file already exists and only checks the return value, assuming that -1 means the file does not exist. However, with large files, stat() fails with "Value too large for defined data type".


Reproduce code:
---------------
<?php
touch("test");
?>

Expected result:
----------------
File "test" remains intact, only file times change.

Actual result:
--------------
File "test" is truncated to 0 (all contents is lost). This only happens when "test" was larger than 2GB.