Create custom template in plugin and display it into post template section?

Question

Right now i am developing a plugin for one of my client according to their need. But I want the plugin hold all the functionality itself including the custom template. I mean my plugin holds the custom template but i don't know that if the template display on the admin post/page section.

Is it possible to display custom template on admin post/page section through plugin? If yes then how? Your help is highly appreciated.

UPDATE:

I have achieved this with old method like create a separate custom template for my plugin so that admin can select the template for the desired plugin. I don't want to provide two separate files for my client, one for plugin and second for theme :(

Answer 1

Page templates are limited to themes by design. Page templates belong to the presentation layer while plugins should do very limited and focused presentation as they can't "know" the presentation implications of their output.

But if you have to do it in a plugin, the better way is to add another box to the page editing screen in which the user can select to use the plugin's temlate for that age, store the value in a meta data and do something like

add_filter('page_template','wpse1223720_template');

function wpse1223720_template($temlate) {
  global $post;

  if (get_post_meta($post->ID,your telmlate meta key) == 'use my temlate')
    return the path to your template file.
  else 
   return $template;
}

Not tested at all. This code interrupts the code that find the appropriate template file to use if the content being served is a page, and makes wordpress use your own template instead of the one associated with the page.

Alternative approach is to run your hook on the template_redirect action and run "manually" your template. You can see and example for this here https://stackoverflow.com/questions/4647604/wp-use-file-in-plugin-directory-as-custom-page-template

Answer 2

Template are usually relegated to theme development and are used to provide layout and presentation which is precisely what themes are meant to provide.

However, you can add a template file to theme when the plugin is activated. You can hook the plugin activation (and deactivation)

register_activation_hook($filename, 'myPluginActivation');
register_deactivation_hook($filename, 'myPluginDeactivation');

and manually create the template files in the theme directory using fopen() fwrite() fclose() (Remember to delete created file on plugin deactivation).

The knows issues of this strategy are:

• if the user change theme the template file doesnt move to new theme directory
• there are no error handling for file operations
• the files that you're giong to create can already exist

If you do not need to leave the choice of template at the client, you can use the template redirect hook and manually redirect the default template with the one in plugin dir.

add_action("template_redirect", 'my_theme_redirect');

function my_theme_redirect() {
  $plugindir = dirname( __FILE__ );
  $return_template = $plugindir . '/themefiles/' . $templatefilename;
  do_theme_redirect($return_template);
}

In this way you override the default template when the plugin is activated. Personally I would use the plugin to create a custom post type and a redirect strategy just for that post type, checking if the custom post type template already exists in theme dir to leave the possibility to create a custom post type template in the theme dir.

You can find useful information in this Tom McFarlin article