Wordpress - If the current user is an administrator or editor

First answer, not WordPress-related because it is just only PHP: Use the logic "OR" operator:

<?php if( current_user_can('editor') || current_user_can('administrator') ) {  ?>
    // Stuff here for administrators or editors
<?php } ?>

If you want to check more than two roles, you can check if the roles of the current user is inside an array of roles, something like:

$user = wp_get_current_user();
$allowed_roles = array('editor', 'administrator', 'author');
<?php if( array_intersect($allowed_roles, $user->roles ) ) {  ?>
   // Stuff here for allowed roles
<?php } ?>

However, current_user_can can be used not only with users' role name, but also with capabilities.

So, once both editors and administrators can edit pages, your life can be easier checking for those capabilities:

<?php if( current_user_can('edit_others_pages') ) {  ?>
    // Stuff here for user roles that can edit pages: editors and administrators
<?php } ?>

Have a look here for more information on capabilities.

First, current_user_can() should not be used to check a user's role - it should be used to check if a user has a specific capability.

Second, rather than being concerned with the user's role but instead focusing on capabilities, you don't have to bother with doing things like the problem asked about in the original question (which is checking if the user is an administrator OR an editor). Instead, if current_user_can() was being used as intended, which is to check for a user's capabilities, not their role, you wouldn't need the conditional check to contain an "or" (||) test. For example:

if ( current_user_can( 'edit_pages' ) ) { ...

edit_pages is a capability of both administrator and editor roles, but not any lower roles such as authors. This is how current_user_can() was intended to be used.

As @butlerblog reply stated, you should not use current_user_can to check against a role

This notice is specifically added in the PHP documentation of has_cap function which is called by current_user_can

While checking against a role in place of a capability is supported in part, this practice is discouraged as it may produce unreliable results.

The CORRECT way to do this is to get the user and check the $user->roles, like this:

if( ! function_exists( 'current_user_has_role' ) ){
    function current_user_has_role( $role ) {

        $user = get_userdata( get_current_user_id() );
        if( ! $user || ! $user->roles ){
            return false;
        }

        if( is_array( $role ) ){
            return array_intersect( $role, (array) $user->roles ) ? true : false;
        }

        return in_array( $role, (array) $user->roles );
    }
}

Here's some helper functions I use to do this (as sometimes i don't want just current user):

if( ! function_exists( 'current_user_has_role' ) ){
    function current_user_has_role( $role ){
        return user_has_role_by_user_id( get_current_user_id(), $role );
    }
}

if( ! function_exists( 'get_user_roles_by_user_id' ) ){
    function get_user_roles_by_user_id( $user_id ) {
        $user = get_userdata( $user_id );
        return empty( $user ) ? array() : $user->roles;
    }
}

if( ! function_exists( 'user_has_role_by_user_id' ) ){
    function user_has_role_by_user_id( $user_id, $role ) {

        $user_roles = get_user_roles_by_user_id( $user_id );

        if( is_array( $role ) ){
            return array_intersect( $role, $user_roles ) ? true : false;
        }

        return in_array( $role, $user_roles );
    }
}

Then you can just do this:

current_user_has_role( 'editor' );

or

current_user_has_role( array( 'editor', 'administrator' ) );