How to display a different image size for mobile

WordPress wp_is_mobile() can be the function that you’re looking for.

// Use the build-in function if WP
if(wp_is_mobile()) // On mobile
{
    the_post_thumbnail_url('featured-image-mobile');
}
else
{
    the_post_thumbnail_url('featured-image');
}

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)