php变量在ajax请求中溢出

Question

This is a theoretical question. I know exactly what's going wrong, I just don't see a way around it.

I'm calling calling php page B from php page A in an ajax request and submitting a query in php page B. I'm trying to get the data back to php page A as a json_encoded array. The problem is that the json variable is overflowing (maxing out the memory_limit).

As a result I'm getting an exception:

[object Object] parsererror SyntaxError: JSON.parse: unexpected character

If I wasn't trying to get this data back as a json_encoded array for purposes of displaying it, I would just echo the data to the screen rather than store it in the variable. But, since I need to get that data back as a json_encoded array, I kind of have to store it.

The only solution I can think of is to simply echo the data out on php page B and change the way I'm handling the date on page A (i.e. not expecting json as the dataType).

Is there any other possible way (barring limiting the rows returned from the query)?

EDIT: I also don't want to change any of the settings in the php.ini. There has to be a clever solution without mucking around with settings.

Answer 1

Use pagination to request the data from the server. Essentially, you'll request n results at a time, until you reach a page number that returns 0 results. So, instead of requesting 20k records at once, you'll request 1000 records 20 times in succession (or whatever number you page your data at).

var resultArr = [];
var url = "foo.php";

function handleData(data) {
    // do stuff with data here
    console.log(data);
}

function getData(url,page) {
    $.ajax(url,{data: { page: page}, type: "GET", dataType:"json"}).done(function(data){
        if (data.length != 0) {
            resultArr = resultArr.concat(data);
            getData(url,page+1);
        }
        else {
            handleData(resultArr);
        }
    });
}   

getData(url,0);

And for your query, limit it to n rows starting with $_GET["page"]*n+1