'Fatal error: Can't use function return value in write context' when passing value from one php file to another

Question

I need to pass a value from this button (proyek.php):

<form method="post" action="setidproyek.php">
  <button type="submit" class="btn btn-success btn-sm" name="idpro" value="<?php echo $list['id_proyek']; ?>"><i class="fas fa-folder-open"></i> Buka</button>
</form>

To this php file (setidproyek.php):

<?php
  session_start();
  $_SESSION('idproyek') = $_POST['idpro'];
  header('laporanmingguan.php');
?>

But I got an error.

Answer 1

Try to use this instead

<form method="post" action="setidproyek.php">
    <input type="hidden" name="idpro" value="<?php echo $list['id_proyek']; ?>" />
    <button type="submit" class="btn btn-success btn-sm" ><i class="fas fa-folder-open"></i> Buka</button>
<form>