Description:
------------
Smarty uses a rather complex variable method name replacement system.  In the "compiled" Smarty templates there is code like this:

  $this->_plugins['function']['assign'][0](/* params */)

Which works fine in PHP4, but PHP5 issues a fatal error:

  "Fatal error: Method name must be a string"

Is this a PHP5 bug or an abuse of PHP syntax (and therefore a Smarty bug)?

Reproduce code:
---------------
A Smarty compiled template:

<?php $this->_load_plugins(array(
array('function', 'assign', 'sql/db-init/Control.tpl', 1, false),)); ?><?php echo $this->_plugins['function']['assign'][0](array('var' => 'fname','value' => "sql/db-init/".$this->_tpl_vars['targetDatabase']."/createdb.tpl"), $this) ; ?>

<?php $_smarty_tpl_vars = $this->_tpl_vars;
$this->_smarty_include($this->_tpl_vars['fname'], array());
$this->_tpl_vars = $_smarty_tpl_vars;
unset($_smarty_tpl_vars);
 ?>
~

Expected result:
----------------
No error.

Actual result:
--------------
Fatal error: Method name must be a string in templates_c/%%-16/%%-1662958972/Control.tpl.php