how to run php script every 5 minutes
It would not surprise me that a hosting service would protect its servers from getting overloaded with long-running scripts, and would configure a time-out after which such scripts are aborted (see PHP: Runtime Configuration Settings and max_execution_time in particular).
If you have a PC that can stay turned on, an alternative solution would be to let it send a request to the server every 5 minutes:
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