如何在javascript中访问php SESSION变量[重复]

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I'm trying to create an image uploading website. In this, when a user logs in, I set a $_SESSION['id'] variable in php. Now, I wish to check if $_SESSION['id'] is set in my javascript file (general.js) in order to carry out certain functions. How should I go about doing it?

</div>
<?php $session_value=(isset($_SESSION['id']))?$_SESSION['id']:''; ?>
    <html>
    <head>
    <script type="text/javascript">
    var myvar='<?php echo $session_value;?>';
    </script>
    <script type="text/javascript" src="general.js"></script>
    </head>
    <body>

    </body>
    </html>

In above code snippet I have initialized global variable myvar with value stored into php session variable into script file before general.js file is referenced in script.It will be accessible in general.js file

A simple example please try this

<?php 
session_start();
$_SESSION['id'] = 12;

?>

<script>
alert(<?php echo $_SESSION['id']; ?>);
</script>

You can even use php variable and array as variable in js like below

<?php
    $id= $_SESSION['id'];
    $data= array('one', 'two', 'three');
?>
<script type="text/javascript">
    var idr = '<?php echo $id; ?>';
    var datar = <?php echo json_encode($data); ?>;
</script>

The best way is to echo the session ID in a javascript variable.

<script>
  var sessionId = "<?php echo $_SESSION['id']; ?>";

  // Your javascript code goes here
</script>

Here PHP is server-Side execution and JavaScript is Client side execution. and $_SESSION is a server-side construct.So probably you can not access that directly using JavaScript You would need to store that variable in $_COOKIE to be able to access it client-side.

You can get that Session using PHP, and then use that for the JavaScript like this

<?php
$variablephp = $_SESSION['category'];
?>

<script>
var variablejs = "<?php echo $variablephp; ?>" ;
alert("category = " + variablejs);
</script>

Here you are getting Session like echo $variablephp using PHP, and the assign that value to JavaScript variable.