使用PHP跟踪文本文件中的更改

I have a PHP script that has to reload a page on the client (server push) when something specific happens on the server. So I have to listen for changes. My idea is to have a text file that contains the number of page loads for the current page. So I would like to monitor the file and as soon as it is modified, to use server push in order to update the content on the client. The question is how to track the file for changes in PHP?

You could do something like:

<?php
while(true){
    $file = stat('/file');
    if($file['mtime'] == time()){
        //... Do Something Here ..//
    }
    sleep(1);
}

This will continuously look for a change in the modified time of a file every second. If you don't constrain it you could kill your disk IO and may need to adjust your ulimit.

This will check your file for a change:

<?php
  $current_contents = "";  

  function checkForChange($filepath) {
    global $current_contents;

    $new_contents = file_get_contents($filepath);
    if (strcmp($new_contents, $current_contents) {
      $current_contents = $new_contents;
      return true;
    }

    return false;
  }

But that will not solve your problem. The php file that serves the client finishes executing before the rendered html is sent to the client. That client will need to call back to some php file to check for a change... and since that is also a http request, the file will finish executing and forget anything in memory.

In order to properly solve this, you'll probably have to back off the idea of checking a file. Either the server needs to know when and how to contact currently connected clients, or those clients need to poll a lightweight service at a regular interval.

This is sort of hacky but what about creating a cron job that sucks in the page, stores it in a scope or table, and then simply compares it every 30 seconds?