从javascript，onload调用php函数（AJAX？）

I have been searching for almost an hour without finding proper example to fix my problem: I would like to call a PHP function (it's a simple unlink with the path given from a javascript function that's executed on page load). I am not good at all with AJAX and I would like to understand how to call directly the PHP function, contained in the index.php file, from the javascript code.

Here's what I have in my javascript code snippet:

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","/dev/templates/absolu/index.php?s=" + Math.random(),true);
//@unlink(listeImages[i].toString());

You send the function name (in case you will have more functions in the future) and params as get params

var fileToDelete;
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","/dev/templates/absolu/index.php?s=" + Math.random()+"&action=delete&file="+fileToDelete,true);

On your PHP script, you should handle it:

<?php
if (isset($_GET['action'])){
  switch($_GET['action']){  
     case 'delete':
       @unlink(listeImages[$_GET['action']].toString());
     break;
     //Other functions you may call
  }
  exit;
}
//The rest of your index.php code
?>

Using jquery (http://jquery.com/) you could make the call as:

$(document).ready(function() {
  $.get("/dev/templates/absolu/index.php?", {
    'action': 'delete',
    'other': 'get-parameters',
    'r': Math.random()
  });
});

Server side example:

<?php

switch( $_GET['action'] ) {
  case 'delete': 
    // call unlink here
  break;
  case 'dosomething':
    // else
  break;
  default: 
    // Invalid request
  break;
}

Please note that deleting files should be handled responsibly (enforce security checks) to make sure no wrong file gets accidentally or on purpose deleted.

You can't call directly a php function from an ajax call, it will only call the php script like if you were opening the page index.php from a browser.

You have to add tests in your php script to know which function has to be called, eg. :

If you call in ajax the page /dev/templates/absolu/index.php?mode=delete_image&image=filename.png

<?php
if($_GET['mode'] == "delete_image") {
    unlink($_GET['image']);
}
?>

Please take care that anybody could call this page so you have to check what will be deleted and to verify what you receive in GET parameters. Here i could call /dev/templates/absolu/index.php?mode=delete_image&image=index.php to delete the php script page.