I’m writing a telegram bot to delete spam from a channel where the bot is administrator (with permission to delete messages)

I want to capture referral links when a Telegram user share my bot’s link.

I just created a bot in Telegram and deploy webhook a PHP file to respond to user’s commands. There is a problem with this code that can’t get a parameter in the shared url for start bot.
it works fine when user start bot in normal way with normal URL (https://t.me/xxxx_bot) but I’m adding a referring part to my code to allow users get points based refers. So I need to make some URLs for users like https://xxxx_bot/?start=123456789, I could manage to create the refer link for each users, but when another users click this shared URL, and want to start bot, the bot can’t get the start parameter’s value.

I am creating a Telegram bot for my store with PHP.