PHP函数 替换指定出现次数的子字符串

/**
 * @name str_seq_replace(($heystack,$search,$to,$seq))
 * @author tunpishuang <tunps .COM>
 * @param $heystack 目标搜索字符串
 * @param $search  关键字
 * @param $to      替换为
 * @param $seq   替换匹配关键字的次序,从0计数
 * @return string 替换后的字符串
 */
function str_seq_replace($heystack,$search,$to,$seq){
    $arrStar=array();
    $sequence=0;
    $strCompare=null;
    $arr=str_split($heystack);
    foreach($arr as $k=>$v){
        $len=strlen($search);
        while($len>0 && $k<count ($arr)){
            $strCompare.=$arr[$k++];
            $len--;
        }
        if($strCompare === $search) $arrStar[]=$k-strlen($search);
        $strCompare=null;
    }
    $replacedStr=substr_replace($heystack,$to,$arrStar[$seq],strlen($search));
    return $replacedStr;
}

例子：

str_seq_replace("fdafdsafsa胡萝卜fdsafdsafdsaf胡萝卜fdsafdsa胡萝卜fdafdsa","胡萝卜","敏感词",0);

结果：

dafdsafsa敏感词fdsafdsafdsaf胡萝卜fdsafdsa胡萝卜fdafdsa

str_seq_replace("fdafdsafsa胡萝卜fdsafdsafdsaf胡萝卜fdsafdsa胡萝卜fdafdsa","胡萝卜","敏感词",2);

fdafdsafsa胡萝卜fdsafdsafdsaf胡萝卜fdsafdsa敏感词fdafdsa