javascript method onclick is executing even submit button is not yet clicked

Im new to php and javascript so please bear with me.

index.php:

<?php
 $_SESSION['test'] = 1;
?>

<div>
 <?php echo "Before: " . $_SESSION['test']; ?>
 <input type="submit" value="CLICK" onclick="<?php $_SESSION['test'] = 0; ?>;" />
 <?php echo "After: " . $_SESSION开发者_开发问答['test']; ?>
</div> 

Why is it that $_SESSION['test'] is already 0 when I haven't clicked the button yet??? Please help me...

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PHP is a preprocessor. Everything you write in PHP is executed BEFORE the page is presented, while javascript executes clientside as the page is running. Therefore, you cannot set a PHP value with a javascript event.

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PHP is a server-side language; it is parsed and run before anything is even sent to the browser. It does not interact with JavaScript.

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You will need to use AJAX to call the php set the session on click via javascript. I suggest having a look at XMLHTTPRequest: http://www.w3.org/TR/XMLHttpRequest/ , or if you don't want to read all of that and learn it, I suggest looking at a javascript library such as http://www.jquery.com, which should simplify what you need to do.

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You need to call session_start() before anything can be stored in the session.

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The way you are trying to do it is impossible.

Use AJAX