Code to add template to page

Question

A plugin creates a set of pages and a template. There must be some method to assign the template to one of the pages. I've attempted to adapt the method shown at filter reference template_include without success.

The page slug is member-register, the template file name is member-content-template.php.

Some of the things that don't work include:

• locate_template(): I suspect that because the template was created by a plugin it is not found by a function that appears to only search themes.
• is_page(): If given the argument of the page's title, slug or id returns false.

Edit:

As I have little experience with WordPress, I work in small increments to see what yields results. Attempts include such things as:

$template = locate_template(['member-content-template.php']);
var_dump($template);die;

Which results in string(0) "" Or:

   $is = is_page(3350);
    var_dump($is);die;

Which results in bool(false) The same is also true for is_page('member-register') and is_page('Register')

If any of the above had yielded acceptable results I would have built a callback as suggested in the filter reference.

Edit #2:

Code snippets:

rma.php (the plugin code)

$page_definitions = array(
...
'member-register' => array(
    'title' => __('Register', 'rma-member-auth'),
    'content' => '[custom_register_form]', 
    'class' => 'Rma\Pages\Register',
    'function' => 'createRegisterForm',
    'template' => 'Rma\Templates\member-content-template.php',
),
);
...
    $templater = new PageTemplater($templates);
    add_action('plugins_loaded', array('Rma\Templates\PageTemplater', 'get_instance'));
    $pages = new PageLoader();
    $pages->pageCreator($page_definitions);
    $pages->shortcodeGenerator($page_definitions);
...

PageLoader:

...
public function pageCreator($page_definitions) {
    foreach ($page_definitions as $slug => $page) {
        // Check that the page doesn't exist already
        $query = new \WP_Query('pagename=' . $slug);
        if (!$query->have_posts()) {
            // Add the page using the data from the array above
            wp_insert_post(
                    array(
                        'post_content' => $page['content'],
                        'post_name' => $slug,
                        'post_title' => $page['title'],
                        'post_status' => 'publish',
                        'post_type' => 'page',
                        'ping_status' => 'closed',
                        'comment_status' => 'closed',
                        'post_template' => $page['template'],
                    )
            );
        }
    }
}

Answer 1

locate_template function searches your current theme's folder for template name(s). If your templates are in a root folder of your theme, use:

$template = locate_template( 'member-content-template.php' );

otherwise, precede the name of a template with subfolder's name ( no slash in front ):

$template = locate_template( 'templates/member-content-template.php' );

To load a template ( if found ) add true as a second parameter of locate_template function:

$template = locate_template( 'member-content-template.php', true );

Update: To load a tempate in your plugin, use filter 'template_include':

function my_template_loader_filter() {
    function my_template_loader( $template ) {
        $my_template = locate_template( 'member-content-template.php.php' );
        if ( ( '' != $my_template ) && is_page( 'member-register' ) )
            return $my_template ;
        }
        return $template;
    }
    add_filter( 'template_include', 'my_template_loader' );
}
add_action( 'after_setup_theme', 'my_template_loader_filter' );

Answer 2

As I seem to have just learned, a page created in a plugin is not considered a page for purposes of adding a template. Instead, I found that the following additions worked:

rma.php:

$id = get_page_by_title('Register')->ID;
$pages->updateRegisterTemplate($id);

and, in PageLoader:

public function updateRegisterTemplate($id) {
    $meta_key = '_wp_page_template';
    $meta_value = './member-content-template.php';

    return update_post_meta($id, $meta_key, $meta_value)
}