使用php

Question

我的网站是这样的： 用户的余额存储在名为currency的列下的数据库中。他赚取足够的钱后赚取货币，然后转到另一页获取账户以换取这些货币。我设置了所有东西，但是一小时后我就烦恼了。如果用户有足够的货币并且他检索了一个帐户，他可以刷新并检索另一个帐户，即使他没有足够的货币我的系统仍然在火狐上给他他的帐户但不在Chrome上（有浏览器我到目前为止已经测试过）我用session，ajax和php来处理交付，这里是代码： 1.在下面的文件中：我检查用户有多少货币并分配一个能力会话，然后在检索帐户时进行检查。用户可以获得货币金额为250或1000或2500的账户，我正在检查他可以在账户中拥有多少货币：

<?php session_start();

unset($_SESSION["ability"]);
$unames = $_SESSION['username'];
$link = mysql_connect( "localhost", "database-username", "database-password");
mysql_select_db("database-name", $link);
$currencyquery = mysql_query("SELECT currency FROM users WHERE username = '$unames'", $link);
while ($row = mysql_fetch_array($currencyquery)) {
    $currencyamount = $row['currency'];  
}
if ($currencyamount<250){
    $_SESSION["ability"]= 'zero';
    echo $_SESSION["ability"];
}
elseif ($currencyamount<1000) {
    $_SESSION["ability"]= 'one';
    echo $_SESSION["ability"];
}
elseif ($currencyamount<2500) {
    $_SESSION["ability"]= 'two';
    echo $_SESSION["ability"];
} 
else {
    $_SESSION["ability"]= 'three';
    echo $_SESSION["ability"];
}
 ?>

然后我有jquery文件监听这个php文件，因为它的echos，如果用户有1的能力允许他获得250个货币的账户，如果他有2：1000货币的能力，如果他有3：2500货币的能力。如果他有能力0，他在尝试时不会获得任何帐户，它会提醒他刷新，如果他试图获得两个或更多帐户而不刷新（这是因为我想在页面加载时取消设置会话然后再设置它们，因为能力可能会改变）该脚本还会删除用户从数据库中获得的每个帐户。

$(document).ready(function () {
var ability = 'zero';
var click = 0;
$.ajax({url: "ability.php"}).done(function( html ) {
    ability = html
    });
    $('#currency2500').click(function(){
        if (click==0){
            if (ability != 'zero') {
                function show_account() {
            $.ajax({
                type: "POST",
                url: "select1.php",
                data:{action:"showroom"},
                success: function (data) {
                    $('#accountinfo').html(data);
                }
            });
        }

        show_account();
        click = click + 1;
            }
        } else if(ability == 'zero') {
            alert("You dont have the required amount of currencies.");
            } else {
                alert('Refresh the page');
                }

    });
    $('#currency250').click(function(){
        if(click==0){
            if (ability != 'zero') {
                var id=$(this).data("id3");

            $.ajax({
                url:"delete1.php",
                method:"POST",
                data:{id:id},
                dataType:"text",
                success:function(data){
                    show_account();
                }
            });
            }
        } else if(ability == 'zero') {
            alert("You dont have the required amount of currencies.");
            }
    });
    $('#currency1000').click(function(){
        if(click==0){
            if (ability != 'zero' && ability != 'one') {
                function show_account() {
            $.ajax({
                type: "POST",
                url: "select2.php",
                data:{action:"showroom"},
                success: function (data) {
                    $('#accountinfo').html(data);
                }
            });
            }

            show_account();
            click = click + 1;
            }
        } else if(ability == "zero" || ability == "one") {
            alert("You dont have the required amount of currencies.");
            } else {
                alert('Refresh the page');
                }
    });
    $('#currency1000').click(function(){
        if(click==0){
            if (ability != 'zero' && ability != 'one') {
                var id=$(this).data("id3");

            $.ajax({
                url:"delete2.php",
                method:"POST",
                data:{id:id},
                dataType:"text",
                success:function(data){
                    show_account();
                }
            });
            }
        } else if(ability == "zero" || ability == "one") {
            alert("You dont have the required amount of currencies.");
            }
    });
    $('#currency2500').click(function(){
        if(click==0){
            if (ability == 'three'){
                function show_account() {
            $.ajax({
                type: "POST",
                url: "select3.php",
                data:{action:"showroom"},
                success: function (data) {
                    $('#accountinfo').html(data);
                }
            });
            }

            show_account();
            click = click + 1;
        }
    } else if(ability != 'three') {
            alert("You dont have the required amount of currencies.");
            } else {
                alert('Refresh the page');
                }
    });
    $('#currency2500').click(function(){
        if(click==0){
            if (ability == 'three'){
                var id=$(this).data("id3");

            $.ajax({
                url:"delete3.php",
                method:"POST",
                data:{id:id},
                dataType:"text",
                success:function(data){
                    show_account();
                }
            });
        }
    } else if(ability != 'three') {
            alert("You dont have the required amount of currencies.");
            }
    });
});

这是用于向用户提供250种货币的帐户的php文件，还有1000,2500的相同值，只更改了250。如果它被jquery调用：

<?php
   session_start();
  $link = mysqli_connect( 'localhost', 'database-username',    'database-password', 'database' );   
  $action=$_POST["action"];
   if($action=="showroom") {
    $query="SELECT * FROM tablename LIMIT 1";
    $show = mysqli_query($link, $query) or die("Error");
    echo "<p id='paragraph' style='font-size:22px;font-weight: bold;'>Here is your 250 currencies account:</p>";
    echo "<table style='position:relative;bottom:30px;' border='2px'><tr><td>Email</td><td>id</td></tr>";
    while ($row = mysqli_fetch_array($show)) {
        echo "<tr><td>" . $row['email'] . "</td><td>" . $row['id'] . "</td></tr>";
    }
    echo "</table>";
    $unames = $_SESSION['username'];
    $query2 = "UPDATE users SET currency=currency-250 WHERE username='$unames'";
    $update = mysqli_query($link, $query2);
    $link = mysql_connect( "localhost", "database-username", "database-password");
    mysql_select_db("database", $link);
    $currencyquery = mysql_query("SELECT currency FROM users WHERE username = '$unames'", $link);
    while ($row = mysql_fetch_array($currencyquery)) {
        $currencyvalue = $row['currency'];  
    }
    unset($_SESSION['currencynumber']);
    $_SESSION["currencynumber"]=strval($currencyvalue);
}

＆GT;

然后是用户进入的页面:(只有一部分来自）

<?PHP
session_start();
 if( !isset($_SESSION['username']) ) {
    header ("Location: login.html");
   }
  <div id="accountinfo"></div>
  <input type="button" id="currency2500" value="Get 2500 currencies" />
   <input type="button" id="currency1000" value="Get 1000 currencies" />
   <input type="button" id="currency250" value="Get 250 currencies" />

所以：如果使用firefox：我可以刷新2-4次，直到我再也无法获得帐户，获得这些帐户后我的余额将为负数。也许有一种方法，如果余额变为负数取消操作并且不向用户显示任何内容？或者如何解决？我正在使用会话来跟踪。