smarty/libs/sysplugins/smarty_internal_extension_loadplugin.php

<?php

/**
 * Smarty Extension Loadplugin
 *
 * $smarty->loadPlugin() method
 *
 * @package    Smarty
 * @subpackage PluginsInternal
 * @author     Uwe Tews
 */
class Smarty_Internal_Extension_LoadPlugin
{
    /**
     * Takes unknown classes and loads plugin files for them
     * class name format: Smarty_PluginType_PluginName
     * plugin filename format: plugintype.pluginname.php
     *
     * @param \Smarty $smarty
     * @param  string $plugin_name class plugin name to load
     * @param  bool   $check       check if already loaded
     *
     * @return bool|string
     * @throws \SmartyException
     */
    public static function loadPlugin(Smarty $smarty, $plugin_name, $check)
    {
        // if function or class exists, exit silently (already loaded)
        if ($check && (is_callable($plugin_name) || class_exists($plugin_name, false))) {
            return true;
        }
        // Plugin name is expected to be: Smarty_[Type]_[Name]
        $_name_parts = explode('_', $plugin_name, 3);
        // class name must have three parts to be valid plugin
        // count($_name_parts) < 3 === !isset($_name_parts[2])
        if (!isset($_name_parts[2]) || strtolower($_name_parts[0]) !== 'smarty') {
            throw new SmartyException("plugin {$plugin_name} is not a valid name format");
        }
        // if type is "internal", get plugin from sysplugins
        if (strtolower($_name_parts[1]) == 'internal') {
            $file = SMARTY_SYSPLUGINS_DIR . strtolower($plugin_name) . '.php';
            if (isset($smarty->_is_file_cache[$file]) ? $smarty->_is_file_cache[$file] : $smarty->_is_file_cache[$file] = is_file($file)) {
                require_once($file);
                return $file;
            } else {
                return false;
            }
        }
        // plugin filename is expected to be: [type].[name].php
        $_plugin_filename = "{$_name_parts[1]}.{$_name_parts[2]}.php";

        // loop through plugin dirs and find the plugin
        foreach ($smarty->getPluginsDir() as $_plugin_dir) {
            $names = array($_plugin_dir . $_plugin_filename, $_plugin_dir . strtolower($_plugin_filename),);
            foreach ($names as $file) {
                if (isset($smarty->_is_file_cache[$file]) ? $smarty->_is_file_cache[$file] : $smarty->_is_file_cache[$file] = is_file($file)) {
                    require_once($file);
                    return $file;
                }
                if ($smarty->use_include_path && !preg_match('/^([\/\\\\]|[a-zA-Z]:[\/\\\\])/', $_plugin_dir)) {
                    // try PHP include_path
                    $file = Smarty_Internal_Get_Include_Path::getIncludePath($file);
                    if ($file !== false) {
                        require_once($file);
                        return $file;
                    }
                }
            }
        }
        // no plugin loaded
        return false;
    }
}