php字符串过长中间省略

/*
     * 描述 : 字符串过长中间省略
     * 参数 :
     *      $string  字符串
     *      $max     字符串多长时开始替换
     *      $rep     替换样式
     * 返回 : 处理后的字符串
     * 作者：kelvin 2017-01-06
     * */
    public function strMiddleReduceWordSensitive($string, $max = 42, $rep = '...') {
        $strlen = strlen($string);
        if ($strlen <= $max) return $string;

        $lengthtokeep = $max - strlen($rep);
        $start = 0;
        $end = 0;

        if (($lengthtokeep % 2) == 0) {
            $start = $lengthtokeep / 2;
            $end = $start;
        } else {
            $start = intval($lengthtokeep / 2);
            $end = $start + 1;
        }

        $i = $start;
        $tmp_string = $string;
        while ($i < $strlen) {
            if (isset($tmp_string[$i]) and $tmp_string[$i] == ' ') {
                $tmp_string = substr($tmp_string, 0, $i) . $rep;
                $return = $tmp_string;
            }
            $i++;
        }

        $i = $end;
        $tmp_string = strrev ($string);
        while ($i < $strlen) {
            if (isset($tmp_string[$i]) and $tmp_string[$i] == ' ') {
                $tmp_string = substr($tmp_string, 0, $i);
                $return .= strrev ($tmp_string);
            }
            $i++;
        }
        return substr($string, 0, $start) . $rep . substr($string, - $end);
    }