You have limited control over your resources on these services
Since you’re just an end-user of such services – you have limited control (if any) over resources and assets.
Website builders have the sole discretion to enable gzip compression or not, when to set expires headers (if at all), how to order JavaScript, and more.
For obvious reasons, you don’t have the ability to edit these options or settings, and thus achieving 100% scores on a website builder is unlikely.
Currently, Wix only supports adding HTML code, which can be added through the HTML element . Wix Code, which uses Javascript , also allows the use of Java Script Libraries when using the HTML element. It is not possible to add PHP code to your Wix site.
Wix websites do not support PHP, only Wix Code. WixCode understands all of Javascript, except for anything that accesses the DOM. This keeps the user from inadvertently “breaking” something