How to prevent skip login direct Access backstage

How to prevent skip login direct access Backstage!

Is it wrong to write?
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After the user logs in, write a unique sessionid to the user, such as $_session[' UID ', and then enter the background, first determine whether $_session[' UID '] exists and is not empty
------to solve the idea----------------------
In general, the login feature is written to the session variable, and then the need to check whether the variable exists to complete the user access to the judgment.
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After the login verification is successful

$_session["user_name"]= $this->username;

Other pages

if (!isset ($_session[' user_name '))
{
    Jump back to landing page
}

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