Description:
------------
If exec is used to start a command that outputs only a single byte, and if the $output array is used, the byte is added twice to the output array.

Tested with php 5.3.1 in cli mode on Windows 2003 Server and Ubuntu 9.10 Server.

This behaviour was introduced with bugfix to #49847:

From exec.c:125
while (php_stream_get_line(stream, b, EXEC_INPUT_BUF, &bufl)) {
...
if (b[bufl - 1] != '\n' && !php_stream_eof(stream)) {
...
continue;

If only a single byte is read, php_stream_eof(stream) returns true, thus no second loop will take place.

After line 149:
while (l-- && isspace(((unsigned char *)buf)[l]));

buflen is 1 and l is 0, therefor

line 160:
if ((type == 2 && bufl && !l) || type != 2) {

yields true and the buffer is added to the output array, again.

Reproduce code:
---------------
<?php
$command = "echo x";
exec( $command, $output );
print_r( $output );

Expected result:
----------------
Array
(
    [0] => x
)

Actual result:
--------------
Array
(
    [0] => x
    [1] => x
)