Why is my php page showing an error on the <?php tags-CodePudding

I am trying to create a webpage which only uses PHP (there does not need to be any HTML elements) but when I run the page I get the following error:

Here is the code for my page:

<script>
<?php
    if(isset($_COOKIE['string']) and isset($_COOKIE['studentarrays'])){
        $string = $_COOKIE['string'];
        $array = explode(",",$string);
        array_shift($array);
        $studentstring = $_COOKIE['studentarrays'];
        $studentarrays = explode(",",$studentstring);

?>
    var array = <?php echo $studentarrays ?>;
    alert(array);
<?php
    }
?>
</script>

What have I done wrong?

Edit: As someone pointed out I had a SESSION variable without starting the session, so this part of the error has now been fixed. Also I had forgotten to include the session code when I copied my code to this website, sorry for the confusion. Thank you for all the replies, it seems that I have made a fair few mistakes with this page so I have decided to go back and simplify this page as much as possible, removing anything which I did not need. Here is my new code:

<script>
<?php
    include"databaseconnection.php";
    session_start();

    if(isset($_COOKIE['studentarrays'])){
        $studentstring = $_COOKIE['studentarrays'];
        $studentarrays = explode(",",$studentstring);
        $teacherid = $_SESSION['username'];
    }
?>
</script>

This seems to be working without errors now but I do not know exactly what it was causing the error. I will update this post if I figure out what part if the original code was causing the error, until then please ignore this question

CodePudding user response：

If you want to passing arrays(php) to JS using JavaScript Object Notation(JSON).

Using json_encode() function: The function can take both single dimensional and multidimensional arrays.

const array = JSON.Parse("<?php echo json_encode($studentarrays) ?>");
    alert(array);

const array = "<?php echo json_encode($studentarrays) ?>";
    console.log(array);

And also you can use PHP implode() function: implode() function is used to build a string that becomes an array literal in JavaScript.

<?php
  
// Creating a PHP Array
$studentarrays = array('John', 'Foo', 'Bar');
  
?>
const array = "<?php echo '["' . implode('", "', $studentarrays) . '"]' ?>";
    console.log(array);

CodePudding user response：

You can't echo on array.

If you want to assign PHP array to json array directly, it's not possible I guess. You could try using JSON, like this:

<script>
<?php
    if(isset($_COOKIE['string']) and isset($_COOKIE['studentarrays'])){
        $string = $_COOKIE['string'];
        $array = explode(",",$string);
        array_shift($array);
        $studentstring = $_COOKIE['studentarrays'];
        $studentarrays = explode(",",$studentstring);

?>
    var array = JSON.parse("<?php echo json_encode($studentarrays) ?>");
    alert(array);
<?php
    }
?>
</script>

Also, the error tells you that your $_SESSION is not defined, have you started session in this file/request cycle?

CodePudding user response：

Try check array contents using empty() instead of isset()