smarty模板变量不清楚

Question

I am trying to understand developing web apps with PHP and smarty this is the book

there is a file departments_list.tpl

{* departments_list.tpl *}
{load_presentation_object filename="departments_list" assign="obj"}
{* Start departments list *}

<div class="box">
  <p class="box-title">Choose a Department</p>
  <ul>
      {* Loop through the list of departments *}
      {section name=i loop=$obj->mDepartments}
        {assign var=selected value=""}
        {* Verify if the department is selected to decide what CSS style to use *}
        {if ($obj->mSelectedDepartment == $obj->mDepartments[i].department_id)}
        {assign var=selected value="class=\"selected\""}
        {/if}
        <li>
        {* Generate a link for a new department in the list *}
        <a {$selected} href="{$obj->mDepartments[i].link_to_department}">
        {$obj->mDepartments[i].name}
        </a>
        </li>
      {/section}
  </ul>
 </div>
{* End departments list *}

I do not understand in above file one line which is

      {section name=i loop=$obj->mDepartments}

how does name=i works I what is i initialized to and how can a loop start from i,

secondly above file is using a file function.load_presentation_object.php

<?php
// Plug-in functions inside plug-in files must be named: smarty_type_name
function smarty_function_load_presentation_object($params, $smarty)
        {
        require_once PRESENTATION_DIR . $params['filename'] . '.php';
        $className = str_replace(' ', '',ucfirst(str_replace('_', ' ',$params['filename'])));
        // Create presentation object
        $obj = new $className();
        if (method_exists($obj, 'init'))
        {
        $obj->init();
        }
        // Assign template variable
        $smarty->assign($params['assign'], $obj);
        }
?>

in above file a parameter $params has been used in last line

        $smarty->assign($params['assign'], $obj);

as far as I can understand from file departments_list.tpl passes on parameter to function.load_presentation_object.php as

{load_presentation_object filename="departments_list" assign="obj"}

so when following is called

function smarty_function_load_presentation_object($params, $smarty)

$params=depratments_list and $smarty=obj

so how does $smarty->assign($params['assign'], $obj);

work what is $params['assign'] in above?

Answer 1

{load_presentation_object filename="departments_list" assign="obj"}

translated to php will be:

smarty_function_load_presentation_object(
    array(
        'filename' => 'departments_list', 
        'assign'   => 'obj'
    ), 
    $smarty
);

Every parameters specified in smarty template are passed as associative array in first argument. Second is always current smarty object.

As for

{section name=i loop=$obj->mDepartments}

it is simple for loop:

for ($i=0; $i < count($obj->mDepartments); $i++) {
    $current = $obj->mDepartments[$i];
}