Description:
------------
wordwrapping suppose that

wordwrap(wordwrap($s,$n,$d),$n,$d) is equal to wordwrap($s,$n,$d) and yes, sometimes php works that way:

$s0 = 'a a a a a a a a';
$s1 = wordwrap($s0,7,'XX');
$s2 = wordwrap($s1,7,'XX');

gives $s1==$s2=='a a a aXXa a a a'


but if we add an extra space to the end of $s0, the result will be
'a a a aXXa a a aXX' != 'a a a aXXa a aXXaXX'


if we construct $s0 as (a )+a? we get $s1!=$s2 if and only if strlen($s0)%8==0. more, the diff between $s1 and $s2 every time is the same: trailing 'XXaXX' in $s2 instead of ' aXX' in $s1.


----------------------------

now lets take a look at the case of 1-char-length thing as the 3rd argument to wordwrap


$s0 = 'a a a a a a a a a a a'; // as above, $s0 is constructed as (a )+a?
$s1 = wordwrap($s0,5,'X');
$s2 = wordwrap($s1,5,'X');

here we only get $s1==$s2 having strlen($s0)<11!


this bug is related to line 828 in /php-src/branches/PHP_5_3/ext/standard/string.c?revision=287264:

current line: 	laststart = lastspace = current;
should be:		laststart = lastspace = current+1;

+1 is obviuos: if we found a breakchar in the string, we can forget about everything to the left of it INCLUDING itself and restart the whole algorythm at the NEXT character as the first character in our new string. so the very first `laststart = lastspace = 0;` to start becomes `laststart = lastspace = current+1;` to restart. this patch completely removes the strange behaviour.



when strlen(3rd argument to wordwrap)>1 another section of code works and the above patch doesnt affect it

Reproduce code:
---------------
<?
function f( $len, $breakstr, $n) {
	echo "\n-------- \$len=$len, \$breakstr='$breakstr', \$n=$n -------\n";
	for ( $i=1, $c = 'a ', $s0='', $x=1, $k=0; $i<=$n; $i++) {
		$s0 .= $c[$x^=1];
		$s1 = wordwrap($s0,$len,$breakstr);
		$s2 = wordwrap($s1,$len,$breakstr);
		if ($s1==$s2) {
			$k++;
			continue;
		}
		echo "strlen(\$s0)=$i -> FAIL\n";
	}
	if ($k==$n) {
		echo "passed all, no fails\n";
	}
}
f(5,'X',20);
f(7,'XX',50);
?>

Expected result:
----------------
-------- $len=5, $breakstr='X', $n=20 -------
passed all, no fails

-------- $len=7, $breakstr='XX', $n=50 -------
passed all, no fails


Actual result:
--------------
-------- $len=5, $breakstr='X', $n=20 -------
strlen($s0)=11 -> FAIL
strlen($s0)=12 -> FAIL
strlen($s0)=13 -> FAIL
strlen($s0)=14 -> FAIL
strlen($s0)=15 -> FAIL
strlen($s0)=16 -> FAIL
strlen($s0)=17 -> FAIL
strlen($s0)=18 -> FAIL
strlen($s0)=19 -> FAIL
strlen($s0)=20 -> FAIL

-------- $len=7, $breakstr='XX', $n=50 -------
strlen($s0)=8 -> FAIL
strlen($s0)=16 -> FAIL
strlen($s0)=24 -> FAIL
strlen($s0)=32 -> FAIL
strlen($s0)=40 -> FAIL
strlen($s0)=48 -> FAIL