Can you please share that website & PHP Code to review?
To Be Honest, there is no a shortcut to Migrate the PHP code to Shopify code. We must write the new code for the Shopify.
Please let me know your availability to discuss further.
I'm Owner of one of India Based Company & have my own in-house team. So I can provide you with One Stop Solution for this project & others too.
We've been working for 7+ years & well equipped in Core PHP, MYSQL, JavaScript, JQuery, Ajax, HTML5, CSS2/3, Bootstrap.
We've 4 years of experience in Shopify. We're well educated about what customization can be possible & what can't. We've extensive experience to build the Shopify website with custom scripts, app integration. We've expertise in Payment Gateway Integration like - PayPal, Stripe, Brain-tree, etc.
PSD/Sketch/Ai to (Full Responsive) Shopify Site
Custom & Responsive theme Design
Installing & Configuring ready-made Shopify Themes
Shopify Themes & Customization
Shopify Apps/Plug-ins Development & Customization
Custom Shopify Apps/plug-in development
Payment Gateways integration
3rd party Shopify App/API integration like social networks, CRM & others.
Cross Browser Compatibility (IE, Firefox, Chrome, Opera, UC & Safari).
We are fully confident to do your task as you desired and believe honesty and hard working on a right path can make satisfy to you.
Look forward to hearing back from you.
Best,
Vipin