我是PHP的初学者，无法设置路径

please help me to use path with php tag with folder name self define.

<?php
  /* Uploadify */

  // Define a destination
  $targetFolder = <?php echo base_url();?>'uploads'; // here is the problem

  if (file_exists($_SERVER['DOCUMENT_ROOT'] . $targetFolder . '/' . $_POST['filename'])) 
    {
      echo 1;
    } 
  else 
    {
      echo 0;
  }
?>

Looks like someone gave this answer in the comments section - adding the full updated code here in the answer for clarity:

<?php
  /* Uploadify */

  // Define a destination
  $targetFolder = base_url() . 'uploads'; // notice no nested PHP tags

  if (file_exists($_SERVER['DOCUMENT_ROOT'] . $targetFolder . '/' . $_POST['filename'])) 
  {
      echo 1;
  } 
  else 
  {
      echo 0;
  }