Run query on specific admin options page and send results to select field in another function

Question

How do I run a get_posts query on an individual options page for my plugin and send those results to another function to populate the select fields?

I'm building a custom plugin that builds a vcard from custom fields on various post types.

On my options page, generated by CMB2, loaded on cmb2_admin_init, I have various select fields that show meta_keys I've found from running a query against all post types. I am seeing a huge number in queries naturally as the entries grow inside each post type. Therefore, I only want to run that query when on the specific admin options page. That is the only time I need that query.

I have been trying to use the 'load-{options-page.php}' action hook which works fine, but I don't understand how to run that query and then get the results inside the function firing on cmb2_admin_init. They are both inside a class so maybe I can pass a variable? But ti always seems to re-run the query because the variable gets assigned inside the function firing on cmb2_admin_init.

I can run this method on 'load-[name-of-optins-page.php}'

/**
 * Convert to array for CMB2 field type
 * @since  0.1.0
 */
public function get_meta_keys_array() {
    $options = array();
    // Get keys from a WP_Query
    $fields = $this->get_meta_keys();
    if( $fields ) {
        // Builds simple array to populate my select fields
        foreach( $fields as $field => $key ) {
            $options[$key] = $key;
        }
    } 
    return apply_filters( 'vcard_get_meta_keys_array_output', $options );
}

and then this function for the field display on 'cmb2_admin_init'

/**
 * Registers options page menu item and form.
 *
 * @since    1.9.0
 */
public function register_options_metabox() {

    // This is where I am running into trouble.
    $meta_keys = $this->get_meta_keys_array();  

    $cmb_options = new_cmb2_box( array(
        'id'           => 'vcard_generator_metabox',
        'title'        => esc_html__( 'vCard Generator Settings', $this->plugin_name ),
        'object_types' => array( 'options-page' )


        $cmb_options->add_field( array(
            'name'             => esc_html__($person['name'], $this->plugin_name),
            'id'               => 'vcard_generator_metabox' . $person['id'],
            'type'             => 'select',
            'show_option_none' => true,
            'default'          => 'custom',
            'options'          => $meta_keys // This is where the meta_keys are populated
        ) );

}

Note that these functions are truncated and will not work with copy/paste

Answer 1

If I’ve understood this correctly, the answer is a simple one.

If these are both in the same class, set a property on your class for storing the output of the first function that runs. From there, any subsequent functions can access the data stored on that property.

Answer 2

1. Instead of iterating over every post, you could use query on meta table with distinct.

   SELECT DISTINCT meta_key FROM wp_postmeta;

This will be faster and more efficient, DISTINCT is expensive though. https://codex.wordpress.org/Custom_Queries

2. You can not make this query always. Save the query results in a transient variable. https://codex.wordpress.org/Transients_API If the variable is not set, make the query store the result in transient.