Description:
------------
When using php://memory stream, attempting to seek behind the start position, produces incorrect results.

Sample test case below (in the next field)

Test case should print the entire stream (all the bytes in the stream, but it prints an empty string.



Test script:
---------------
<?php
$fh = fopen('php://memory', 'w');

for ($ii = 0; $ii < 10; $ii++) {
   fwrite($fh, "[$ii] hello world. ");
}

$sz = 170;

fseek($fh, $sz - 100, SEEK_SET);

fseek($fh, -$sz, SEEK_CUR);

var_dump(fread($fh, $sz));
?>


Expected result:
----------------
string(170) "[0] hello world. [1] hello world. [2] hello world. [3] hello world. [4] hello world. [5] hello world. [6] hello world. [7] hello world. [8] hello world. [9] hello world. "

Actual result:
--------------
string(0) ""