How can different domains on the same server affect PHP session handling?

Different domains on the same server can affect PHP session handling because by default, PHP sets the session cookie to be specific to the domain it was accessed on. This means that if you have multiple domains pointing to the same server, the session cookie may not be shared across them. To solve this issue, you can set the session cookie domain to a common root domain that all your domains share.

// Set the session cookie domain to a common root domain
ini_set('session.cookie_domain', '.yourdomain.com');