Description:
------------
When using preg_replace with a pattern of '/(.*)/' or similar, the returned string will contain two instances of the replacement text, with the second instance appended to the first and given empty backreferences.

This behavior does not occur when the pattern is anchored to the start of the string: '/^(.*)/'.

./configure --with-apxs --enable-versioning --enable-memory-limit --with-mysql=/usr --enable-xslt --with-xslt-sablot --with-gd --with-jpeg-dir=/usr --with-zlib-dir=/usr --with-ttf=/usr --with-freetype-dir=/usr --enable-gd-native-ttf --enable-bcmath --with-mime-magic

Reproduce code:
---------------
<?php
echo preg_replace('/(.*)/', 'a$1b', 'foo') ."\n";
echo preg_replace('/(.*)$/', 'a$1b', 'foo') ."\n";
echo preg_replace('/^(.*)/', 'a$1b', 'foo') ."\n";
echo preg_replace('/^(.*)$/', 'a$1b', 'foo') ."\n";
echo preg_replace('/.*/', 'ab', 'foo') ."\n";
echo preg_replace('/f*/', 'ab', 'foo') ."\n";
?>

Expected result:
----------------
afoob
afoob
afoob
afoob
ab
aboo

Actual result:
--------------
afoobab
afoobab
afoob
afoob
abab
ababoaboab