代码如下:
function text2links($str='') {
    if($str=='' or !preg_match('/(http|www\.|@)/i', $str)) { return $str; }
    $lines = explode(\n, $str); $new_text = '';
    while (list($k,$l) = each($lines)) {
        // replace links:
        $l = preg_replace(/([ \t]|^)www\./i, \\1http://www., $l);
        $l = preg_replace(/([ \t]|^)ftp\./i, \\1ftp://ftp., $l);
        $l = preg_replace(/(http:\/\/[^ )\r\n!]+)/i,
            \\1, $l);
        $l = preg_replace(/(https:\/\/[^ )\r\n!]+)/i,
            \\1, $l);
        $l = preg_replace(/(ftp:\/\/[^ )\r\n!]+)/i,
            \\1, $l);
        $l = preg_replace(
            /([-a-z0-9_]+(\.[_a-z0-9-]+)*@([a-z0-9-]+(\.[a-z0-9-]+)+))/i,
            \\1, $l);
        $new_text .= $l.\n;
    }
    return $new_text;
}