从 Javascript 调用的 PHP 函数不起作用

Question

I am working on a posting system in PHP. The posting system goes through a SQL database and then prints out data from the database. I am trying to use javascript to see if the system has been updated. Basically, I want to use javascript to check whether any new posts have been added. I have some code that goes into the database

function minicheck (){
    $query= "SELECT * FROM posts";
    $result= mysql_query($query);
    return mysql_num_rows($result);
}

The function returns the number of rows in the database every 10 seconds.I use javascript to call this function.

<?php
     echo(" <script>
        killPage();
        function killPage () {
      setInterval(function(){
    x++;
    alert(".minicheck().");
    }, 10000);
     }
   </script> ");
?>

THe issue i am facing is that the function returns the exact same value no matter whether or not a row has been added into the sql databse. Even if I add a row into the sql database, the value that is returned by this function is the exact same every time.

How can I fix this?

Thank You,.

Answer 1

You cannot call PHP functions from JavaScript like that.

What you are doing is calling the function once when building your JavaScript, which is then being sent to the browser.

The browser only ever gets the static value you've put in the string, so naturally it can never update.

If you want to call something in PHP from JavaScript, you'll probably want to use XMLHttpRequest (or any of the readily available libraries like jQuery that can help w/AJAX) to query a PHP file that runs the function and returns the value.