Display custom post metadata that start with universal prefix

WP API | Display custom post metadata

// --- WP-API | Display all custom post metadata that start with 'xxx_' --- //
function wmi_past_poss_custom_metadata( $post_response, $post, $context ) {
    $meta = get_post_custom( $post['ID'] );
    $custom_fields = array();
    foreach ( $meta as $key => $value ) {
        // Replace 'xxx_' with any custom metakey prefix (ie. '_' for private metakey's)
        if ( 'xxx_' !== substr( $key, 0, 1 ) ) {
            $custom_fields[ $key ] = $value;
        }
    }
    $post_response['custom_fields'] = $custom_fields;
    return $post_response;
}
add_filter( 'json_prepare_post', 'wmi_past_poss_custom_metadata', 10, 3 );
// --- Complements of https://github.com/WP-API/WP-API/issues/367 --- This was lost, now it's found ;)//
// --- END WP-API | Display all custom post metadata that start with 'xxx_' --- //