# Create Plugin-Filter (en)

Summary

Create Plugin-Filter (en) |
Create and install a Plugin-Filter | Plugin-Filter are module-like ZIP-packages build from the files plugin_info.php, plugin_install.php, filter.php

### Create and install a Plugin-Filter

Plugin-Filter are module-like ZIP-packages build from the files plugin_info.php, plugin_install.php, filter.php and maybe plugin_uninstall.php.

The following tokens can be used instead of hardcoded pathes within OpF-Plugins

>     {SYSVAR:WB_URL}   = will replace with the content of the Constant WB_URL
>     {SYSVAR:WB_PATH}  = will replace with the content of the Constant WB_PATH
>     {OPF:PLUGIN_URL}  = will replace with WB_URL.'/modules/outputfilter_dashboard/plugins/{your_plugin}'
>     {OPF:PLUGIN_PATH} = will replace with WB_PATH.'/modules/outputfilter_dashboard/plugins/{your_plugin}'

inside the filter functions the following CONSTANTS work with OPF Plugins

>     OPF_PLUGINS_PATH
>     OPF_PLUGINS_URL

the path and url to the plugins folder is very long and is being used extensivly in Filters, therefore the constants are a convenient addition. The URL is

>     OPF_PLUGINS_URL = [ WB_URL.'/modules/'.basename(dirname(__FILE__)).'/plugins/' ]

#### plugin_info.php

>     <?php
>     $plugin_directory   = 'cachecontrol';
>     $plugin_name        = 'Cache Control';
>     $plugin_version     = '1.0.0';
>     $plugin_author      = 'author...';
>     $plugin_license     = 'GNU General Public License, Version 2 or later';
>     $plugin_description = 'Filter to automatically prevent browsers from delivering outdated files (css,js) from cache';

#### plugin_install.php

See opf_register_filter().

>     <?php
>     if(!defined('WB_PATH')) die(header('Location: ../../index.php'));

>     opf_register_filter(array(
>             'plugin' => 'cachecontrol',
>             'name' => 'Cache Control',
>             'type' => OPF_TYPE_PAGE_LAST,
>             'file' => '{OPF:PLUGIN_PATH}/filter.php',
>             'funcname' => 'opff_cachecontrol',
>             'desc' => array('EN' => "Description ... Take care that this filter is called last!",
>                             'DE' => "Beschreibung ... Achten Sie darauf, daß dieser Filter als letzter aufgerufen wird!"
>             ),
>             'modules' => 'all',
>             'active' => 1,
>             'allowedit' => 0,
>             'allowedittarget' => 1
>     ));

By default during installation filters are appended to the end of the list, but you can influence the position later on using the function opf_move_up_before.

#### filter.php

This file contains the filter-function itself. See The Filter-Function itself.

>     <?php
>     if(!defined('WB_PATH')) die(header('Location: ../../index.php'));

>     function opff_cachecontrol(&$content, $page_id, $section_id, $module, $wb) {
>             // function code here

>             return(TRUE);
>     }

#### plugin_uninstall.php

This file is optional, and can be omitted.

>     <?php
>     if(!defined('WB_PATH')) die(header('Location: ../../index.php'));

>     // clean up.
>     // But do NEVER CALL opf_unregister_filter() in this file!

> function opf_register_filter( | $filter, |  |
> | $serialized | = | FALSE | )

Register a new Filter.

> function opf_move_up_before( | $name, |  |
> | $ref_name | = | "" | )

Upon registration move a filter up to a position before another one.
The Filter function must have an unique name, and should have a “opff_”-prefix
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