Is a bitcoin wallets balance calculated on the client computer app? eg. Leger Live
How is bitcoin wallet balance calculated cryptographically?
There's no cryptography involved, certainly no encryption.
You add the credits and subtract the debits.
Does Ledger Live app check/compare each transaction+hash & transaction+signature hash like mempool ...
Is it possible to do this in PHP?
So far as Bitcoin is concerned, I believe it is probably possible.
For example, by looking at https://en.bitcoin.it/wiki/PHP_developer_intro I can see
The easiest way to get started is to run Bitcoin in daemon mode with which PHP communicates via local HTTP requests. A library called JSON-RPC is used to call the various ...