从javascript更新数据库表

Question

I want to update my database after a condition in javascript. What I do now is something like:

 <a href="#" onclick="hello()">Update me</a>

<srcipt>
function hello(smthing)
{
 if(smthing == true)
 {
   <?php //Update database table ?>
 }
}
<script>

I have also tried to update my table according an example in w3schools (http://www.w3schools.com/ajax/ajax_example.asp):

<script>

function hello(smthing)
{
   if(smthing==true)
   {
      var xmlhttp;
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }

xmlhttp.open("GET","db_update.php",true);
xmlhttp.send();
   }
}

</script>

In the first case it updates my table even if the variable smthing = false (but if i enter an alert("hi") inside the if, the alert will be displayed only if 'smthing' is true.

In the second case nothing happens. :/

Any help or guidance pls?

Answer 1

Javascript is client side scripting language.So it cannot communicate directly with database.

Only Server side scripting language can interact with database through its library functions.

So if you need to update data in database on condition of javascript variable you can accomplish it using ajax technology.

Through AJAX code snippet it can communicate with server in background without reloading the web page using XMLHttpRequest Object.

Please refer the example mentioned in following URL which uses ajax technique for communication with database

http://www.w3schools.com/php/php_ajax_database.asp