JSON新手 - 在浏览器重新加载之间永久保存值为JSON

I have an AJAX poll based on this tutorial: http://www.w3schools.com/php/php_ajax_poll.asp

However, instead of writing the poll entries from the HTML radio button to an array in a text file (as outlined in the tutorial). I would like to write to a JSON file. At the moment the values from the radio button entry are sent to the JSON, but the file does not retain the value between browser refreshes. I think that this is probably an issue with my syntax or encoding - the server should have the correct permissions to write to the file. Any tips are greatly appreciated.

<?php $vote = $_REQUEST['vote'];
//get content of json
$filename = "poll.json";
$poll = file_get_contents($filename);
$json = json_decode($poll);
//put content in array
$array = explode("||", $content[0]);
$yes = $array[0];
$no = $array[1];
if ($vote == 0) {
$yes = $yes + 1;
}
if ($vote == 1) {
$no = $no + 1;
}
//insert votes to json file
$insertvote = $yes."||".$no;
$fp = fopen($filename,"w");
fputs($fp,$insertvote);
$poll = json_encode($json);
fclose($fp);?>

At the moment the result is either: {1||} or {||1} in the JSON file, I can't figure out how to save the values the way that they were saved to the .txt file version (as outlined here: http://www.w3schools.com/php/php_ajax_poll.asp)

Update

So based on the excellent advice I received I am much closer. I found that "w" was the correct option for the php as "a+" appended data in the JSON rather than updating the existing values.

I now have a JSON file which is updating the values that are added through the html radio buttons.

So the result looks like: [3,4] AKA 3 votes from option 1 and 4 votes for option 2

Several issues:

  • You JSON format is not JSON. Values like 0||1 are not JSON, and so json_encode on it will fail. One of the benefits of true JSON is that you don't have to juggle with delimiters like ||.
  • The $content variable is nowhere initialised.
  • You encode something as JSON near the end, but don't do anything with it.
  • You call a variable $json when you intend to store decoded JSON in it. That is really confusing. Don't call such a variable $json.

Here is some alternative code:

$vote = $_REQUEST['vote'];
//get content of json
$filename = "poll.json";
if (!file_exists($filename)) { // First time ever
    $poll = [0, 0];
} else {
    $poll = json_decode(file_get_contents($filename));
    if (!$poll) $poll = [0, 0];
}
// increment counter for vote
$poll[$vote] += 1;
//insert votes to json file
file_put_contents($filename, json_encode($poll));

Your problem is at this line:

$fp = fopen($filename,"w");

According to the manual, mode "w":

places the file pointer at the beginning of the file and truncate the file to zero length

In other words: Each request overrides the whole file with it's contents.

To fix this, use mode "a+".

$fp = fopen($filename,"w");

Probably you change code and this is undefined:

$content[0]

In

$array = explode("||", $content[0]);

Source Is:

<?php
$vote = $_REQUEST['vote'];

//get content of textfile
$filename = "poll_result.txt";
$content = file($filename);

//put content in array
$array = explode("||", $content[0]);
$yes = $array[0];
$no = $array[1];

if ($vote == 0) {
  $yes = $yes + 1;
}
if ($vote == 1) {
  $no = $no + 1;
}

//insert votes to txt file
$insertvote = $yes."||".$no;
$fp = fopen($filename,"w");
fputs($fp,$insertvote);
fclose($fp);
?>