retrive from DB without click any button using onfocus - php

Question

hi I have some problem with my code!
I have a textbox when the user write in this text box I want to retrieve from DB directly without clicking any button.
then some of my form will completed after writing in this textbox.
my JS code :
function centerIDfocus()
{
var id = document.getElementById("centerID").value;
var data = <?php $center_ID = echo mysql_num_rows(mysql_query("SELECT * FROM 'examcenter' WHERE 'id' = '".id."'")); ?> ;
}
window.onload = addEventsToHTML;
in my form:
<input name="centerID" id="centerID" onfocus="centerIDfocus();">
and that’s not working!
any ideas red face

Answer 1

You mixed 2 languages - javascript is run on client side and php on server side.
What You need to do is:
var data = function_to_get_data(); // in javascript
in that function call ajax request to the address of your php script - and only in that php script call your database to return desired data

Answer 2

You're PHP code will only run once, when the pages is loaded, after that it won't run again because there's nothing happening on the server side. If you want to run it each time you get the focus then you should be using AJAX.
Take a look at AJAX gets, I'm pretty sure that's what you want:
http://api.jquery.com/jQuery.get/

Answer 3

It is rather hard to know what you are intending to do, but...
My guess is that you are confused about when things happen and when "onfocus" is fired.
PHP is run on the server when the page is being constructed. In contrast, javascript is run in the browser, either after the constructed page has arrived (onload) or in response to a user click or other event such as onfocus.
Thus there is no way for the javascript (in the browser) to drop into PHP (on the server). For the same reason (and security) it is impossible for javascript to talk directly to the database.
There are two approaches you might take to do what (I think) you are attempting to do.
You could create a javascript array in PHP, indexed by ID, and containing all possible IDs and their data. Use PHP to read the database, and then echo the javascript to define the array. This would become part of the page sent. Then, in response to the event that means you want to fill the field, you extract the data from the array, and put it where you want it. This would be slow for the page to load, but very quick response to the click that triggered the change.
An alternative is to use ajax. The easiest way is to use jquery to send a GET request to the the server requesting the data related to the ID. The server must respond to that URL by extractign the ID, reading the database and generating the reply. I recommend using JSON. Then, when the jquery request returns, the javascript code can move the data from the JSON into your field. This would make the initial page lighter, but would have a fetch delay to the triggering click.
However I think you may also have an issue with the on-focus event. This fires when the user moves the cursor into the field, before they have entered any data. At that point it will contain the data that was set in the HTML. If you can set the ID at that point, you can also set it to the data from the database.
I think you want two fields - one for the ID and another for the looked up data. Then you run the javascript on the onblur event on the ID field.
Hope that helps.

Answer 4

use something like:
$('.centerID').keyup(function(){
var val = this.val();
var url = '/do.php'; // url to a php script
var val = 'action=checkValue&value='+val; // send it the value
$.getJSON(url, val, function(data){
// Something to do when you get the data back
});
});
then just create a php script that checks the database and returns a JSON answer and then do as you please with it.
BTW - I'm assuming you are ok using jQuery. You can apply this to your JavaScript too.
I used keyup() as one example but you can appy this to keydown(), click(), focus(), focusout() etc...
I have a do.php script that contains a switch statement with the possible value of action= and returns JSON. Everything from logging in, registering, activity monitor, to updating a database field without leaving the page.