有个关于字符串合并去重问题的可实现性疑惑？

<?php>
        $str = "大家好[81]。你是谁[3]。大家好[3]。老师好[12]。上午好。上午好[12]。";
    $arr = explode ( "。", $str );                        //以"。"为分隔符,存储到数组$arr;
    foreach ( $arr as $key => $values ) {                 // 遍历$arr数组
        parse_str ( $values, $output );                    //把查询字符串解析到变量中  

        foreach ( $output as $key => $values ) {         // 遍历$output数组  其中$values是数组形式存储
            if (empty ( $values )) {                    //对于没有解析到空值,进行手动赋值
                $values [1] = "";
            }
            foreach ( $values as $k => $values ) {        //将$values数组中的键值存储到$tmp2数组中
                $tmp2 [] = $k;                       

            }
            $tmp [] = $key;                                //将output数组中的键值存储到$tmp数组中
        }
    }
    foreach ( $tmp as $key => $values ) {                 // 遍历$tmp数组        $values为字符串
        $a = array_keys ( $tmp, $values );                 // 返回重复值的键名 以数组形式返回
        $b = array();
        foreach ( $a as $v ) {                            //遍历$a数组    通过数组$a中的值将$tmp2中与其相关的值存储到$b数组中
            $b [] += $tmp2 [$v];               

        }
        $re[$values] = array_sum($b);                    //$re数组中的值为相同字符串后面值的和

    }
    foreach ($re as $key => $values){                                 //将结果以固定的结构输出
        echo $key."[".$values."]"."。";
    }
<?>