Help with my encoder

[silent]

Ok, I am writing a system called "FreeLock" (similar to CodeLock)
It works fine, except for when an include is called for...
the encoded script looks like this :

<?php $use_zlib='y'; $script_name='test.php';
include('freelock.php'); exit;?>
ENCRYPTED DATA IS AT THE END OF THE FILE

Here is freelock.php :

<?php
##############################
### FreeLock Include v1.0b ###
### by Brian Gardner       ###
##############################
$freelock_active = 'y'; //so that we know it is already included

function read_script() {
  global $script_name; //set in the running script
  $script = file_get_contents($script_name);
  return $script;
}

function get_enc_script($script) {
  $ex = explode('---B---',$script);
  return $ex[1];
}

// *VERY* simple scramble --- for testing only
function case_swap($input) {
  for($i=0;$i<strlen($input);$i++) {
    if(ereg('[a-z]',$input[$i])) {
	  $input[$i] = strtoupper($input[$i]);
	} else if(ereg('[A-Z]',$input[$i])) {
	  $input[$i] = strtolower($input[$i]);
	} else {}
  }
  return $input;
}

function decode_xlate($input) {
  return case_swap($input);
}

function decode_script($script) {
  global $use_zlib;
  $script = decode_xlate($script);
  if($use_zlib == 'y') {
    $script = gzinflate(base64_decode($script));
  } else {
    $script = base64_decode($script);
  }
  return $script;
}

function freelock_run() {
  eval(decode_script(get_enc_script(read_script())));
}

if($freelock_active == 'y') {
freelock_run();
}
?>

Any ideas? I am using include_once now, and tried calling the freelock_run() function explicitly, but it causes PHP to crash Apache...

I'm at a loss here. An encoder isn't much good if it can't include files, is it?

Thanks in advance.