Description:
------------
Take the test script below and save it as UTF-8 and verify:

> cat test.php | tail -n 4 | head -n 1 | hexdump -C
00000000  09 23 20 c3 a4 c3 b6 0a                           |.# .....|
00000008

Now run

> ./bin/php test.php | hexdump -C
PHP Version = 5.4.8
zend.multibyte = 1
00000000  58 00 00 00                                       |X...|
00000004

As you can see PHP added three NUL bytes to the file.
Now remove one of the characters in the commented out line:

> ./bin/php test.php | hexdump -C
PHP Version = 5.4.8
zend.multibyte = 1
00000000  58 00 00                                          |X..|
00000003

As you can see the NUL bytes are directly related to the amount of non-ASCII characters in the file.

Now comment out the declare statement:

> ./bin/php test.php | hexdump -C
PHP Version = 5.4.8
zend.multibyte = 1
00000000  58                                                |X|
00000001

This time the output is correct.

Tested with off-the-shelf PHP, but also happens with ubuntu packaged 5.4.6-1
Also happends when PHP is running as Apache module where this issue caused corrupted images for me.

Test script:
---------------
<?php
	declare(encoding='UTF-8');

	fwrite(STDERR,"PHP Version = ".phpversion()."\n");
	fwrite(STDERR,"zend.multibyte = ".ini_get('zend.multibyte')."\n");

	# äöü
	echo "X";

?>


Expected result:
----------------
See above.
UTF-8 declared files with UTF-8 content should work fine.

Actual result:
--------------
See above.
UTF-8 declared files with UTF-8 content produce NUL bytes in the output.