PHP incrementing serverside counter

Question

I'm making a webpage that (mostly) lets users increment a counter. I can read the file with jQuery .load() just fine, but writing to it is proving difficult.

Relevant code:

HTML

  <button onclick="add();">increment</button>
  <p>counter value: <span id="c"></span></p>
  <script src="https://code.jquery.com/jquery-3.6.3.min.js" integrity="sha256-pvPw+upLPUjgMXY0G+8O0xUf+/Im1MZjXxxgOcBQBXU=" crossorigin="anonymous"></script>
  <script>
    $(function() {
      $("#c").load("c.txt");
    });
    function add() {
      $.get("add.php");
      $("#c").load("c.txt");
    }
  </script>

add.php

<?php
  $file = fopen("c.txt", "w");
  $c = fread($file, filesize("c.txt"));
  fwrite($file, (int)$c + 1);
  fclose($file);
?>

c.txt
0 or 47 or your favorite positive integer

I'm not sure what I'm doing wrong here.

Fermin Perdomo · Accepted Answer · 2023-02-10 23:13:52Z

1

the problem is you are trying to call an async function as not sync behavior. So you must change the add method to call $.get and use the callback response from the server to load your file again example:

function add() {
      $.get("add.php", function (dataFromTheServer) {
      $("#c").load("c.txt");
    });     
}

A better alternative is to receive the count directly from the serve so you don't have to do another request to update the count example:

HTML

<button onclick="add();">increment</button>
  <p>counter value: <span id="c"></span></p>
  <script src="https://code.jquery.com/jquery-3.6.3.min.js" integrity="sha256-pvPw+upLPUjgMXY0G+8O0xUf+/Im1MZjXxxgOcBQBXU=" crossorigin="anonymous"></script>
  <script>
    $(function() {
      $("#c").load("c.txt");
    });
    function add() {
      $.get("add.php", function (data) {
       $("#c").text(data);
    });
      
    }
  </script>

also, you have to open the file to read and write using w+ PHP: add.php

<?php
  $file = fopen("c.txt", "w+");
  $c = fread($file, filesize("c.txt"));
  fwrite($file, (int)$c + 1);
  fclose($file);
echo $c;
?>

answered Feb 10, 2023 at 23:13

Fermin Perdomo

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1 Comment

mí ebı Over a year ago

Tried this and it just outputted the php file (and didn't write to c.txt)

Marco · Accepted Answer · 2023-02-10 23:10:19Z

0

I would solve the add.php this way:

<?php
  $c = file_get_contents("c.txt");
  file_put_contents("c.txt", (int)$c+1);
?>

Adopted from the exmaple here: https://www.php.net/manual/en/function.file-put-contents.php

answered Feb 10, 2023 at 23:10

Marco

3,6574 gold badges28 silver badges38 bronze badges

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