Hi @jamie.richards ,
The problem is if the user has not logged in via the portal, loginWithRedirect then prompts them to login within the 3rd party app.
I think that what you may be looking for is to set your php central login portal as a custom identity provider which would have to be registered in your Auth0 tenant as a custom connection and allowed for your apps. And for the login with redirect → authorization params → you would set the connection=name_of_your_custom_IdP so users that are not logged in would be redirected there.
This article describe the scenario - Connect Apps to Generic OAuth2 Authorization Servers
You could also search the library of the Auth0’s sdk in use to see what methods are available to check the user session. For example, checkSession() relies on auth0 cookies stored in the end user browser.
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