Description:
------------
ftell() reports the size of bytes added to a file instead of the position of the file pointer in the file.
I guess this behavior is reproduceable only on appending data to a file, since on new files the file pointer position is at the same place of the number of bytes added.

Reproduce code:
---------------
<?php
# Adding something to the test-file to see the behavior
$fp = fopen("test", w);
fwrite($fp, "Ciao");
fflush($fp);
fclose($fp);
# test-file saved and closed

# Opening a file with non-zero size (just added some bytes)
$fp = fopen("test", a);
fwrite($fp, "Ciao");
fflush($fp);
$s = filesize("test");
$t = ftell($fp);
print("The pointer should be at the position $s, but ftell reports $t");
fclose($fp);
?>


Expected result:
----------------
The pointer should be at the position 8, but ftell reports 8

Actual result:
--------------
The pointer should be at the position 8, but ftell reports 4