say CR LF carriage return and line feed, yes those characters could
be trimmed, I think it's a choice to keep the original input you could
redefine a function if your are no happy with it or even add an
optional param to the C function: bool preserveCRLF, I am not really
convinced by Scott argument 8-)

hi, all:

I just found a typo today when I read the source code of function nl2br,
here is what 'svn diff' produce against the php 5.3.0 svn trunk:

Index: ext/standard/string.c

--- ext/standard/string.c       (revision 290364)
+++ ext/standard/string.c       (working copy)
@@ -3918,7 +3918,7 @@
      tmp = str;
      end = str + str_len;

•       /* it is really faster to scan twice and allocate mem once insted
  scanning once

•       /* it is really faster to scan twice and allocate mem once instead
  scanning once
           and constantly reallocing */
        while (tmp < end) {
                if (*tmp == '\r') {

This typo and the grammatical error are fixed now.

besides, I have a question: why not function nl2br just replace the "\r\n",
"\n", "\r" things with "<br/>"? why insert "<br/>" before those "\r\n",
"\n", "\r"?

Because its much easier to read the output when the newlines are preserved.

Scott