Addy Osmani, a Google Chrome engineer, recently published a e-book on image optimization. You can read it in it's entirety here: https://images.guide/

Images take up massive amounts of internet bandwidth because they often have large file sizes. According to the HTTP Archive, 60% of the data transferred to fetch a web page is images composed of JPEGs, PNGs and GIFs. As of July 2017, images accounted for 1.7MB of the content loaded for the 3.0MB average site. Per Tammy Everts, adding images to a page or making existing images larger have been proven to increase conversion rates. It's unlikely that images will go away and so investing in an efficient compression strategy to minimize bloat becomes important.

If you need to optimize images in your PHP application take a look at our image optimization package. If you're a Laravel user you'll be happy to know that there's also a Laravel version of the optimizer. Our Laravel Medialibrary also comes with built-in support for optimizing images.