regex negative look behind not working

[brendan]

Hi ... want to antispam any email address that is written in a page, so long
as it is not already contained in a hyperlink ie 'mailto:us**@email.com'

so am trying to use a negative look behind but I can't get it to work

preg_replace('/(?<!mailto)(([_\\.0-9a-z-]+)@([_\\.0-9a-z-]+))/i',
"<script>document.write('<a
href=\'mailto:'+'\\1'+'@'+'\\2'+'\'>'+'\\1'+'@'+'\ \2'+'</a>');</script>",$st
ring );

doesn't ignore strings starting with mailto (have also tried using
'mailto\\:'

[Chung Leong]

That doesn't work, because the pattern will match again as soon as the
regexp engine looks one letter to the right.

The bracketed letter below indicates the first letter of a possible
match. The following fails the lookbehind assertion, because "mailto:"
matches the condition:

mailto:[c]he**********@hotmail.com

The following does not fail the assertion, as "mailto:c" is not a
match:

mailto:c[h]er*********@hotmail.com
A job like this is easier with preg_replace_callback(), arguably the
most powerful text manipulation function in PHP. Example:

function antispam($m) {
return ($m[1]) ? $m[0] :
"<script>document.write('<a
href=\'mailto:'+'{$m[3]}'+'@'+'{$m[4]}'+'\'>'+'$m[3]'+'@'+'$m[4]'+'</a>');</script>";
}

preg_replace_callback('/(mailto:)?\s*(([_\\.0-9a-z-]+)@([_\\.0-9a-z-]+))/i',
'antispam', $string);

[brendan]

"Chung Leong" <ch***********@hotmail.com> wrote in message
news:11**********************@g44g2000cwa.googlegr oups.com...

That doesn't work, because the pattern will match again as soon as the
regexp engine looks one letter to the right. A job like this is easier with preg_replace_callback(), arguably the
most powerful text manipulation function in PHP. Example:

function antispam($m) {
return ($m[1]) ? $m[0] :
"<script>document.write('<a
href=\'mailto:'+'{$m[3]}'+'@'+'{$m[4]}'+'\'>'+'$m[3]'+'@'+'$m[4]'+'</a>');</
script>"; }

preg_replace_callback('/(mailto:)?\s*(([_\\.0-9a-z-]+)@([_\\.0-9a-z-]+))/i', 'antispam', $string);

Excellent, this works perfectly.