不熟悉业务，写了一个晚上

<?php
header("charset=utf-8;");

function StrToBin($str){
    //1.列出每个字符
    $arr = preg_split('/(?<!^)(?!$)/u', $str);
    //2.unpack字符
    foreach($arr as &$v){
        $temp = unpack('H*', $v);
        $v = base_convert($temp[1], 16, 2);
        unset($temp);
    }

    return join(' ',$arr);
}

function BinToStr($str){
    $arr = explode(' ', $str);
    foreach($arr as &$v){
        $v = pack("H".strlen(base_convert($v, 2, 16)), base_convert($v, 2, 16));
    }

    return join('', $arr);
}

echo StrToBin("哈哈hhh123");
echo '<br/>';
echo BinToStr(StrToBin("哈哈hhh123"));