尝试刷新分配给PHP变量的JavaScript变量

问题描述：

I have assigned two variables that are equal to a PHP variable that can change at any time. I am trying to update a div every 5 seconds; for example, to update the number. I am assuming this doesn't work because the PHP doesn't run again once the page has loaded. What is the best way to get around this? I don't mind linking to another page if necessary. Here's my code:

$(document).ready(function() {
    var buyprice = <?php echo $coinTicker->price($coin2[1] , 'buy'); ?>;
    var sellprice = <?php echo $coinTicker->price($coin2[1] , 'sell'); ?>;
    $('#currentbuyprice').html(buyprice);
    $('#currentsellprice').html(sellprice);
    setInterval(function() {
    var buyprice = <?php echo $coinTicker->price($coin2[1] , 'buy'); ?>;
    var sellprice = <?php echo $coinTicker->price($coin2[1] , 'sell'); ?>;
    $('#currentbuyprice').html(buyprice);
    $('#currentsellprice').html(sellprice);
   }, 5000);
});

答

Yeah - that won't work as you know.

  setInterval(function() {
    var buyprice = <?php echo $coinTicker->price($coin2[1] , 'buy'); ?>;
    var sellprice = <?php echo $coinTicker->price($coin2[1] , 'sell'); ?>;
    $('#currentbuyprice').html(buyprice);
    $('#currentsellprice').html(sellprice);
   }, 5000);

That is a javascript + php. The browser runs javascript and php runs on the server. They run at different times and are mutually exclusive. The work apart from each other.

What you want to do (probably) if you are trying to update realtime is to use an ajax call.
http://api.jquery.com/jquery.ajax/

I find the api documentation good for reference but bad for example.

var jqXHR = $.ajax({
  url: "target.aspx",
  type: "GET",
  dataType: "html",
}).done(function (data, status, jqXHR) {
  $("#container").html(data);
  alert("Promise success callback.");
}).fail(function (jqXHR,status,err) {
  alert("Promise error callback.");
}).always(function () {
  alert("Promise completion callback.");
})

That makes a pretty good example. Google "jqXHR" for other working examples

答

You can't update static PHP variables, because the PHP-script gets an request, works and answers to the client, so the session is closed. The are two ways to handle that.

Way 1: You have to connect your PHP to an Database. So you will send a request to a PHP-file, which updates the numbers in the database, so the values will be safed, also for the next request.

Way2: You can make PHP Sessions php.net link. So you will save your values temporary in a session. That session will deleted after a while, and maybe that is not that, what you need. sessions are similar to cookies.

Both ways work through an AJAX-Request. So you need an Javascript-Function, that will send your request to that PHP-file, which will update the Database or the Session. You should also have a function to get that values from the Database or the Session.

答

$(document).ready(function() {
    var buyprice = <?php echo $coinTicker->price($coin2[1] , 'buy'); ?>;
    var sellprice = <?php echo $coinTicker->price($coin2[1] , 'sell'); ?>;
    $('#currentbuyprice').html(buyprice);
    $('#currentsellprice').html(sellprice);

    setInterval(function() {
        $.get('/get_prices.php', function( data ) {
            buyprice = data.buy;
            sellprice = data.sell;
            $('#currentbuyprice').html(buyprice);
            $('#currentsellprice').html(sellprice);
        }, "json" );
   }, 5000);
});

And in your backend (/get_prices.php in this example, change it!)

<?php
$buy = 1;
$sell = 1;
echo json_encode(array(
    'buy' => $buy,
    'sell' => $sell,
));
exit;

答

You can make a simple ajax get request to a seperate php file that returns the data as json:

setInterval(function() {
    $.get('/prices.php', function(data){
        $('#currentbuyprice').html(data.buyprice);
        $('#currentsellprice').html(data.sellprice);
    });
}, 5000);

prices.php:

//code that creates $cointTicker and $coin vars goes here
header('Content-Type: application/json');
echo json_encode(
         [
             'buyprice'  => $coinTicker->price($coin2[1] , 'buy'),
             'sellprice' => $coinTicker->price($coin2[1] , 'sell')
         ]
      );

答

Using the same approach (making a polling) you can make an ajax query

<!DOCTYPE html>
<html>
<head>
    <title>

    </title>
    <meta charset="utf-8" />
    <meta name="description" content="">
    <meta name="keywords" content="">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <script type="text/javascript" src="http://code.jquery.com/jquery-1.8.3.min.js" charset="UTF-8"></script>
</head>
<body>
    <script>


    function send(){
        $.ajax({
            url: "a.php/",
            type: 'GET',
            success: function(res) {
                var myVars = JSON.parse(res);
                console.log(myVars[0].buyprice);
                $('#currentbuyprice').html(myVars[0].buyprice);
                $('#currentsellprice').html(myVars[0].sellprice);
            }
        });
    }
    setInterval(function(){ send() }, 3000);
    </script>

    currentsellprice:
    <div id="currentbuyprice">

    </div>
    currentsellprice:
    <div id="currentsellprice">

    </div>
</body>

here the minimal part of the server

<?php
    $out = "[";
    $out .= '{"buyprice":"'. time(). '",';
    $out .= '"sellprice":"'. time()/2 . '"}'; 
    $out .="]";
    echo $out; 
?>

You can find a lot of information related with this topics (ajax and json) in internet.

尝试刷新分配给PHP变量的JavaScript变量

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