检索结果高亮显示关键词的函数

函数如下:

function highlight($str, $keywords, $color = "red") {
    if (empty($keywords)) {
        return $str;
    }
    $keywords = split("[ /t/r/n,]+", $keywords);
    $str_begin = "##~~##~";
    $str_end   = "~##~~##";
    foreach($keywords as $val) {
        $tvar = preg_quote($val);
        $tvar = str_replace('/', '//', $tvar);
        $patterns[]    = "/(" . $tvar . ")/";
        $replacement[] = $str_begin . urlencode($val) . $str_end;
        $tvar = preg_quote(urlencode($val));
        $tvar = str_replace('/', '//', $tvar);
        $tmppattern[]  = "/(" . $str_begin . $tvar . $str_end . ")/";
        $finalrep[]    = "<span style='color:" . $color . "'>" . $val . "</span>";
    }
    $str = preg_replace($patterns, $replacement, $str);
    $str = preg_replace($tmppattern, $finalrep, $str);
    return $str;
}