Please try using this CVS snapshot:

  http://snaps.php.net/php5.3-latest.tar.gz
 
For Windows:

  http://windows.php.net/snapshots/

Verified. Actually this may be expected.

<?php
fseek($fp, 0);
var_dump(stream_get_line($fp, 6, "\n"));
?>

If stream_get_line() reads only 5 bytes here there is no way to tell if this is the end of the stream (without re-reading from the stream, which would block on sockets, etc). So it can't find the end of the line and return false.

The next call to stream_get_line() will mark the stream as EOF, and stream_get_line will return the line:

<?php
$fp = tmpfile();
fwrite($fp, '12345');
fseek($fp, 0);

while (!feof($fp)) {
 $line = stream_get_line($fp);
 if ($line === false) continue;
 var_dump($line);
}
?>

Result:
string(5) "12345"

Thanks for your feedback.  I tried it on the latest PHP 5.3 snapshot and got the same results.

I noticed though when I run this:

<?php
fseek($fp, 0);
var_dump(fgets($fp, 6));

fseek($fp, 0);
var_dump(fgets($fp, 7));
?>

I get the expected results of:

string(5) "12345"
string(5) "12345"

Since the manual page for stream_get_line() states that this function is identical to fgets() except for handling of the delimiter, should stream_get_line() return the same results as fgets() for this case since my delimiter is a newline?

Also, I'm not sure why these 2 calls to stream_get_line() return different output:

<?php
fseek($fp, 0);
var_dump(stream_get_line($fp, 6));

fseek($fp, 0);
var_dump(stream_get_line($fp, 6, "\n"));
?>

Result:

string(5) "12345"
bool(false)

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

Because the file is still open there is no EOF, so the stream_get_line() 
cannot find the line's end and there is no EOF, thus it returns false.

Thanks for your reply.  Shouldn't stream_get_line() find the EOF since it will read the first 5 characters and then find the EOF when trying to read the next character since $length = 6?  Also, if what you wrote is the case, I'm not sure why this:

<?php
$fp = tmpfile();

fwrite($fp, "12345");

fseek($fp, 0);
var_dump(stream_get_line($fp, 6, "\n"));
?>

returns:

bool(false)

but this works successfully:

<?
$fp = tmpfile();

fwrite($fp, "12345\n67890");

fseek($fp, 0);
var_dump(stream_get_line($fp, 6, "\n"));
var_dump(stream_get_line($fp, 6, "\n"));
?>

returns:

string(5) "12345"
string(5) "67890"

On the 2nd call to stream_get_line(), there are 5 bytes remaining to be read, $length = 6, and there are no \n's remaining, which is the same exact scenario as my first example above.  In my first example, stream_get_line() returns false, but in the 2nd example, stream_get_line() returns the expected string - should both of these calls have the same results?

I encountered this issue when trying to use stream_get_line() to parse very large text files reading in each file in sections delimited by a string delimiter, but one of my text files did not contain this delimiter and stream_get_line() returned false for that file which I don't believe was correct.  I was expecting it to read in the entire file since $length was greater than the size of the file, which is what the documentation says should occur.

Thanks again for your assistance.