let arr = {
aa:aa,
bb:bb
}
function serialize(arr){
var arr_length = 0;
var content = ''
for(var i in arr){
content += 's:'+i.length+':"'+i+'";'
content += 's:'+arr[i].length+':"'+arr[i]+'";'
arr_length++;
}
var str = 'a:' + arr_length +':{'+content+'}'
return str
}