How to check user input in laravel

I have a column input named Address, and how to check, if user input like null, ‘null’ and ” , the return response will be error. I have make it, but it not working.

This is my code:

      $address = $request->input('address');
        if ($address == null) 
        {
            return response()->json(['message'=>'no data','success'=>0]);
        }
        elseif($address == '')
        {
            return response()->json(['message'=>'no data','success'=>0]);
        }
        elseif($address == 'null')
        {
            return response()->json(['message'=>'no data','success'=>0]);
        }
        else 
         //process
        }

Answer

You may use the empty function, which would return FALSE if var exists and has a non-empty, non-zero value. Otherwise returns TRUE. This implies the following conditions considered as empty:

• “” (an empty string)
• 0 (0 as an integer)
• 0.0 (0 as a float)
• “0” (0 as a string)
• NULL
• FALSE
• array() (an empty array)

Snippet for your reference:

$address = $request->input('address');
if(empty($address)){
    return response()->json(['message' => 'no data','success' => 0]);
}