PHP is getting outdated at this point and less and less sites are using it. Most modern gambling sites use some form of JavaScript on the front end (such as AngularJS or React) and many are also using JavaScript on the backend, via node.js.
If you're looking to create a gambling website, I'd recommend avoiding PHP and start learning JavaScript.
I am not in touch with programming anymore (It's been long time) but I thought JavaScript is client site language. It use to improve the user experience but to pull data and save data you need a server side scripting language like: PHP, ASPX etc.
For example: Calculate 3 * 9 which is 27.
You really do not need to save any data here to do this multiplication. Do it in the client side.
Edit:
Did some finding and this is what I found:
https://www.quora.com/Is-it-possible-to-build-website-without-serverside-language-being-usedUgly as hell, but functional!
It worth reading.
Technically, you only need HTML to create a website. It would look like crap, but it can be done.
Add in CSS, and boom, you can make your site look a lot better.
Add in JS (I prefer jQuery) and then you can animate your website.
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All of these things make up a static website. That means, everytime you come to the website, the content never changes.
For example:
http://companysolutionswithben.com always appears the same way. Now, it’s wrote with PHP, and it is driven by the server (because I wanted to use Wordpress) but the same exact thing could have been created as a static website.
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Now, if you want to have users, an eCommerce platform (basically if you want to store data) you’re going to have utilize a server side language.
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For ease:
Static = Never changing (server side not needed)
Dynamic = Constantly changing (server side needed)