Posted by Chung Leong on 09/13/05 23:48

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]hernyshevsky@hotmail.com

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

mailto:c[h]ernyshevsky@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);

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