Linking onClick to PHP Functionality

[Anon]

This is basically syntax.

I have a checkbox :

<input name="chk1" type="checkbox" onClick=FOO_JS() >

This is fine when I put the foo_js() in Javascript with

<?
echo "<script type=Javascript>
function foo_js()
{
....

}
</script>";
?>

However in foo_js I can not access any of my php variables and I cannot
tell the checkbox to set itself to checked or unchecked.

Alternative ? :

Now with this thing I have the functionality :
<?
function foo_php()
{
// do neat things with my php variables
$chk1 = isset($chk1);
}
?>

But in the checkbox doesn't like php functions after onClick :

<input name="chk1" type="checkbox" onClick=FOO_PHP() >

this causes syntak error in my PHP4.

So, is there a way to make an event handler for the checkbox
using any kind of function which would use php variables?

[Anon]

Remember, PHP is server side. Once the html is displayed you can't access php functions. You can pass PHP variables to js variables and then have a js function that takes some action.

[Anon]

I see what you mean. Sort of. Now with this project we have set a bunch of variables as "perenial" so that they don't fade away when a secondary page takes over the screen. These variables are updated each time the main screen comes on. The variables hold an array of items ordered. The secondary screen says "do you really want this new item added" or "do you really want to delete this item", and returns to the main screen (html page) with the arrays correctly modified.
If two people use this now simultaneously then would both perenial php-server side-variables melt into one another since there is only one server and many
users?

And you said I could pass php variables to js variables. Could you generate a
simple example? It is this wall between js and php which I'm trying to break through. The syntax allows me to call a js fuction from a click event on the
checkbox but only JS functions...And what do js functions know about the
php variables floating around?

[Anon]

OK, you're still missing a fundamental point:

PHP is strictly server side. You can't access php variables/functions/anything once the page has been served to the browser.

When a php file is requested by a client, the server passes the file to the PHP interpreter which executes the php code and passes the resultant output to the web server to be sent to the client. Once that happens PHP is no longer a part of the picture. Those PHP variables you had are now NOT variables. They either ceased to exist OR exist ONLY as STATIC data in the HTML.

Now, that said, you can take a PHP variable and assign the value to a js variable in the php script. e.g.:

<?
// do some PHP stuff
?>

..blah
< some tag onClick=jsfunc(<? print $variable ?>)>

What happens is that PHP will replace the <? print $variable ?> with the value of $variable at the time. When it reaches the client it will look like:

< some tag onClick=jsfunc(25)>

if the value of $variable was 25.

The only way you can call a php function based on user input in the client is to make another request to the server.

As, to your question about multiple users. You've delved into the <irony>wonderful</irony> world of STATE.

Web pages are stateless, meaning that they is no way a server can know which client is requesting the page and maintain server information for that client in and of itself. That's up to you to do. You have to pass some sort of information via a cookie, the url in an a href link or in a hidden form field back to the server so that your script there can determine the identity of the client. You used to be able to do this with header information (IP address, etc) but no longer. Maintaining this state is called session management. If you are using PHP4, you can use the built in session management (see the manual for more info). If not you can use an off the shelf component called PHPLIB (PHP4's session management is based on that) or you can roll your own. Session management is nothing more than assigning a unique identifier to each user. Each subsequent request to the server from the same client would pass back that identifier and you can use that in your scripts as an index to store information about the client/user in a flat file or an RDBMS such as MySQL.

HTH

[Anon]

Have a pop-up window in javascript that calls the a php page then modifies contact back on the original page. That is the only way.