如何用PHP实现会话同步？

Question

我正在用PHP开发WebApp。用户单击一个按钮，PHP代码就可以调用系统执行程序。由于WebApp使用AJAX，因此用户有可能单击两次按钮，或者实际上单击另一个按钮启动另一个exec进程。

我知道我可以编写一些JavaScript来禁用按钮，直到单个事件完成为止。但是，客户端强制执行很容易被覆盖。

PHP方面是否可以做一些事情来阻止这种事情的发生？ 我有一个想法，让会话变量充当“信号量”，并且在执行每个脚本之前检查此变量，并且必须返回0才能继续脚本。

这样做正确吗？

Answer 1

You could use jQuery.ajax() and set the option async to false:

async Default: true By default, all requests are sent asynchronously (i.e. this is set to true by default). If you need synchronous requests, set this option to false. Cross-domain requests and dataType: "jsonp" requests do not support synchronous operation. Note that synchronous requests may temporarily lock the browser, disabling any actions while the request is active

You could use it like this:

$.ajax({
    type: "POST",
    url: "file.php",
    async: false,
    data: data,
    success: function(return){
        alert("Success: "+return);
    }
});

If you want to add a loader just apply it as:

startLoader();
$.ajax({
    type: "POST",
    url: "file.php",
    async: false,
    data: data,
    success: function(return){
        alert("Success: "+return);
    }
});
endLoader();

However you PHP idea is simply not a good one. Opening a session and do all the process for this kind of thing is just useless and slow your script down. You should be asking yourself: Do I really need to block this?

If the answer is yes then do this: Create a table called processes in you database. Inside that table create 2 fields: One will be the process identifier: process_id; the second will be the process status: process_status. The first is an integer you will define with sha1(IMAGE). The second will be an integer: 1 for "busy", 0 for "free".

Then you could do something like this:

SELECT process_status FROM vps_processes WHERE process_id = sha1(CURRENT_IMAGE);

And check whatever it is 1 or 0. If it is 1 then block the script; If it is 0 then you query:

UPDATE vps_processes SET process_status = 1 WHERE process_id = sha1(CURRENT_IMAGE);

then run what you have to run and at the end of the script query:

UPDATE vps_processes SET process_status = 0 WHERE process_id = sha1(CURRENT_IMAGE);