Syntax error, unexpected 'if' (T_IF), expecting ']' can someone help me I am stuck

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PHP

hey i want to write a query that will check for balance when you click login and it will show a message that has your balance but if you dont have a balance it will allow you to login in laravel .Below is what i have tried.the list of balance is in another table called defaulters.

What I have tried:

protected function validateLogin(Request $request)
 {
     // "SELECT * from defaulters where myPIN => '$myPIN'"
     // union
     $defaulters = Defaulters_Reg::select('Debt_amount')->where('myPIN',$id)->get();
     $request->validate([
         'myPIN' => 'required|myPIN',
         'Debt_amount' => 'required|string'
         if ($validateLogin->fails())
         {
             return Redirect::to ('login')
         }
     ])

     $request->validate([
         $this->username() => 'required|string',
         'password' => 'required|string',
     ]);
 }